| Message ID | 20200610113515.1497099-4-mst@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | vhost: ring format independence | expand |
On Wed, Jun 10, 2020 at 1:36 PM Michael S. Tsirkin <mst@redhat.com> wrote: > > As testing shows no performance change, switch to that now. > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > Signed-off-by: Eugenio Pérez <eperezma@redhat.com> > Link: https://lore.kernel.org/r/20200401183118.8334-3-eperezma@redhat.com > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > --- > drivers/vhost/test.c | 2 +- > drivers/vhost/vhost.c | 318 ++++++++---------------------------------- > drivers/vhost/vhost.h | 7 +- > 3 files changed, 65 insertions(+), 262 deletions(-) > > diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c > index 0466921f4772..7d69778aaa26 100644 > --- a/drivers/vhost/test.c > +++ b/drivers/vhost/test.c > @@ -119,7 +119,7 @@ static int vhost_test_open(struct inode *inode, struct file *f) > dev = &n->dev; > vqs[VHOST_TEST_VQ] = &n->vqs[VHOST_TEST_VQ]; > n->vqs[VHOST_TEST_VQ].handle_kick = handle_vq_kick; > - vhost_dev_init(dev, vqs, VHOST_TEST_VQ_MAX, UIO_MAXIOV, > + vhost_dev_init(dev, vqs, VHOST_TEST_VQ_MAX, UIO_MAXIOV + 64, > VHOST_TEST_PKT_WEIGHT, VHOST_TEST_WEIGHT, true, NULL); > > f->private_data = n; > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > index 11433d709651..28f324fd77df 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -304,6 +304,7 @@ static void vhost_vq_reset(struct vhost_dev *dev, > { > vq->num = 1; > vq->ndescs = 0; > + vq->first_desc = 0; > vq->desc = NULL; > vq->avail = NULL; > vq->used = NULL; > @@ -372,6 +373,11 @@ static int vhost_worker(void *data) > return 0; > } > > +static int vhost_vq_num_batch_descs(struct vhost_virtqueue *vq) > +{ > + return vq->max_descs - UIO_MAXIOV; > +} > + > static void vhost_vq_free_iovecs(struct vhost_virtqueue *vq) > { > kfree(vq->descs); > @@ -394,6 +400,9 @@ static long vhost_dev_alloc_iovecs(struct vhost_dev *dev) > for (i = 0; i < dev->nvqs; ++i) { > vq = dev->vqs[i]; > vq->max_descs = dev->iov_limit; > + if (vhost_vq_num_batch_descs(vq) < 0) { > + return -EINVAL; > + } > vq->descs = kmalloc_array(vq->max_descs, > sizeof(*vq->descs), > GFP_KERNEL); > @@ -1610,6 +1619,7 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg > vq->last_avail_idx = s.num; > /* Forget the cached index value. */ > vq->avail_idx = vq->last_avail_idx; > + vq->ndescs = vq->first_desc = 0; > break; > case VHOST_GET_VRING_BASE: > s.index = idx; > @@ -2078,253 +2088,6 @@ static unsigned next_desc(struct vhost_virtqueue *vq, struct vring_desc *desc) > return next; > } > > -static int get_indirect(struct vhost_virtqueue *vq, > - struct iovec iov[], unsigned int iov_size, > - unsigned int *out_num, unsigned int *in_num, > - struct vhost_log *log, unsigned int *log_num, > - struct vring_desc *indirect) > -{ > - struct vring_desc desc; > - unsigned int i = 0, count, found = 0; > - u32 len = vhost32_to_cpu(vq, indirect->len); > - struct iov_iter from; > - int ret, access; > - > - /* Sanity check */ > - if (unlikely(len % sizeof desc)) { > - vq_err(vq, "Invalid length in indirect descriptor: " > - "len 0x%llx not multiple of 0x%zx\n", > - (unsigned long long)len, > - sizeof desc); > - return -EINVAL; > - } > - > - ret = translate_desc(vq, vhost64_to_cpu(vq, indirect->addr), len, vq->indirect, > - UIO_MAXIOV, VHOST_ACCESS_RO); > - if (unlikely(ret < 0)) { > - if (ret != -EAGAIN) > - vq_err(vq, "Translation failure %d in indirect.\n", ret); > - return ret; > - } > - iov_iter_init(&from, READ, vq->indirect, ret, len); > - > - /* We will use the result as an address to read from, so most > - * architectures only need a compiler barrier here. */ > - read_barrier_depends(); > - > - count = len / sizeof desc; > - /* Buffers are chained via a 16 bit next field, so > - * we can have at most 2^16 of these. */ > - if (unlikely(count > USHRT_MAX + 1)) { > - vq_err(vq, "Indirect buffer length too big: %d\n", > - indirect->len); > - return -E2BIG; > - } > - > - do { > - unsigned iov_count = *in_num + *out_num; > - if (unlikely(++found > count)) { > - vq_err(vq, "Loop detected: last one at %u " > - "indirect size %u\n", > - i, count); > - return -EINVAL; > - } > - if (unlikely(!copy_from_iter_full(&desc, sizeof(desc), &from))) { > - vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n", > - i, (size_t)vhost64_to_cpu(vq, indirect->addr) + i * sizeof desc); > - return -EINVAL; > - } > - if (unlikely(desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_INDIRECT))) { > - vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n", > - i, (size_t)vhost64_to_cpu(vq, indirect->addr) + i * sizeof desc); > - return -EINVAL; > - } > - > - if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_WRITE)) > - access = VHOST_ACCESS_WO; > - else > - access = VHOST_ACCESS_RO; > - > - ret = translate_desc(vq, vhost64_to_cpu(vq, desc.addr), > - vhost32_to_cpu(vq, desc.len), iov + iov_count, > - iov_size - iov_count, access); > - if (unlikely(ret < 0)) { > - if (ret != -EAGAIN) > - vq_err(vq, "Translation failure %d indirect idx %d\n", > - ret, i); > - return ret; > - } > - /* If this is an input descriptor, increment that count. */ > - if (access == VHOST_ACCESS_WO) { > - *in_num += ret; > - if (unlikely(log && ret)) { > - log[*log_num].addr = vhost64_to_cpu(vq, desc.addr); > - log[*log_num].len = vhost32_to_cpu(vq, desc.len); > - ++*log_num; > - } > - } else { > - /* If it's an output descriptor, they're all supposed > - * to come before any input descriptors. */ > - if (unlikely(*in_num)) { > - vq_err(vq, "Indirect descriptor " > - "has out after in: idx %d\n", i); > - return -EINVAL; > - } > - *out_num += ret; > - } > - } while ((i = next_desc(vq, &desc)) != -1); > - return 0; > -} > - > -/* This looks in the virtqueue and for the first available buffer, and converts > - * it to an iovec for convenient access. Since descriptors consist of some > - * number of output then some number of input descriptors, it's actually two > - * iovecs, but we pack them into one and note how many of each there were. > - * > - * This function returns the descriptor number found, or vq->num (which is > - * never a valid descriptor number) if none was found. A negative code is > - * returned on error. */ > -int vhost_get_vq_desc(struct vhost_virtqueue *vq, > - struct iovec iov[], unsigned int iov_size, > - unsigned int *out_num, unsigned int *in_num, > - struct vhost_log *log, unsigned int *log_num) > -{ > - struct vring_desc desc; > - unsigned int i, head, found = 0; > - u16 last_avail_idx; > - __virtio16 avail_idx; > - __virtio16 ring_head; > - int ret, access; > - > - /* Check it isn't doing very strange things with descriptor numbers. */ > - last_avail_idx = vq->last_avail_idx; > - > - if (vq->avail_idx == vq->last_avail_idx) { > - if (unlikely(vhost_get_avail_idx(vq, &avail_idx))) { > - vq_err(vq, "Failed to access avail idx at %p\n", > - &vq->avail->idx); > - return -EFAULT; > - } > - vq->avail_idx = vhost16_to_cpu(vq, avail_idx); > - > - if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) { > - vq_err(vq, "Guest moved used index from %u to %u", > - last_avail_idx, vq->avail_idx); > - return -EFAULT; > - } > - > - /* If there's nothing new since last we looked, return > - * invalid. > - */ > - if (vq->avail_idx == last_avail_idx) > - return vq->num; > - > - /* Only get avail ring entries after they have been > - * exposed by guest. > - */ > - smp_rmb(); > - } > - > - /* Grab the next descriptor number they're advertising, and increment > - * the index we've seen. */ > - if (unlikely(vhost_get_avail_head(vq, &ring_head, last_avail_idx))) { > - vq_err(vq, "Failed to read head: idx %d address %p\n", > - last_avail_idx, > - &vq->avail->ring[last_avail_idx % vq->num]); > - return -EFAULT; > - } > - > - head = vhost16_to_cpu(vq, ring_head); > - > - /* If their number is silly, that's an error. */ > - if (unlikely(head >= vq->num)) { > - vq_err(vq, "Guest says index %u > %u is available", > - head, vq->num); > - return -EINVAL; > - } > - > - /* When we start there are none of either input nor output. */ > - *out_num = *in_num = 0; > - if (unlikely(log)) > - *log_num = 0; > - > - i = head; > - do { > - unsigned iov_count = *in_num + *out_num; > - if (unlikely(i >= vq->num)) { > - vq_err(vq, "Desc index is %u > %u, head = %u", > - i, vq->num, head); > - return -EINVAL; > - } > - if (unlikely(++found > vq->num)) { > - vq_err(vq, "Loop detected: last one at %u " > - "vq size %u head %u\n", > - i, vq->num, head); > - return -EINVAL; > - } > - ret = vhost_get_desc(vq, &desc, i); > - if (unlikely(ret)) { > - vq_err(vq, "Failed to get descriptor: idx %d addr %p\n", > - i, vq->desc + i); > - return -EFAULT; > - } > - if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_INDIRECT)) { > - ret = get_indirect(vq, iov, iov_size, > - out_num, in_num, > - log, log_num, &desc); > - if (unlikely(ret < 0)) { > - if (ret != -EAGAIN) > - vq_err(vq, "Failure detected " > - "in indirect descriptor at idx %d\n", i); > - return ret; > - } > - continue; > - } > - > - if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_WRITE)) > - access = VHOST_ACCESS_WO; > - else > - access = VHOST_ACCESS_RO; > - ret = translate_desc(vq, vhost64_to_cpu(vq, desc.addr), > - vhost32_to_cpu(vq, desc.len), iov + iov_count, > - iov_size - iov_count, access); > - if (unlikely(ret < 0)) { > - if (ret != -EAGAIN) > - vq_err(vq, "Translation failure %d descriptor idx %d\n", > - ret, i); > - return ret; > - } > - if (access == VHOST_ACCESS_WO) { > - /* If this is an input descriptor, > - * increment that count. */ > - *in_num += ret; > - if (unlikely(log && ret)) { > - log[*log_num].addr = vhost64_to_cpu(vq, desc.addr); > - log[*log_num].len = vhost32_to_cpu(vq, desc.len); > - ++*log_num; > - } > - } else { > - /* If it's an output descriptor, they're all supposed > - * to come before any input descriptors. */ > - if (unlikely(*in_num)) { > - vq_err(vq, "Descriptor has out after in: " > - "idx %d\n", i); > - return -EINVAL; > - } > - *out_num += ret; > - } > - } while ((i = next_desc(vq, &desc)) != -1); > - > - /* On success, increment avail index. */ > - vq->last_avail_idx++; > - > - /* Assume notifications from guest are disabled at this point, > - * if they aren't we would need to update avail_event index. */ > - BUG_ON(!(vq->used_flags & VRING_USED_F_NO_NOTIFY)); > - return head; > -} > -EXPORT_SYMBOL_GPL(vhost_get_vq_desc); > - > static struct vhost_desc *peek_split_desc(struct vhost_virtqueue *vq) > { > BUG_ON(!vq->ndescs); > @@ -2428,7 +2191,7 @@ static int fetch_indirect_descs(struct vhost_virtqueue *vq, > > /* This function returns a value > 0 if a descriptor was found, or 0 if none were found. > * A negative code is returned on error. */ > -static int fetch_descs(struct vhost_virtqueue *vq) > +static int fetch_buf(struct vhost_virtqueue *vq) > { > unsigned int i, head, found = 0; > struct vhost_desc *last; > @@ -2441,7 +2204,11 @@ static int fetch_descs(struct vhost_virtqueue *vq) > /* Check it isn't doing very strange things with descriptor numbers. */ > last_avail_idx = vq->last_avail_idx; > > - if (vq->avail_idx == vq->last_avail_idx) { > + if (unlikely(vq->avail_idx == vq->last_avail_idx)) { > + /* If we already have work to do, don't bother re-checking. */ > + if (likely(vq->ndescs)) > + return 1; > + > if (unlikely(vhost_get_avail_idx(vq, &avail_idx))) { > vq_err(vq, "Failed to access avail idx at %p\n", > &vq->avail->idx); > @@ -2532,6 +2299,41 @@ static int fetch_descs(struct vhost_virtqueue *vq) > return 1; > } > > +/* This function returns a value > 0 if a descriptor was found, or 0 if none were found. > + * A negative code is returned on error. */ > +static int fetch_descs(struct vhost_virtqueue *vq) > +{ > + int ret; > + > + if (unlikely(vq->first_desc >= vq->ndescs)) { > + vq->first_desc = 0; > + vq->ndescs = 0; > + } > + > + if (vq->ndescs) > + return 1; > + > + for (ret = 1; > + ret > 0 && vq->ndescs <= vhost_vq_num_batch_descs(vq); > + ret = fetch_buf(vq)) > + ; (Expanding comment in V6): We get an infinite loop this way: * vq->ndescs == 0, so we call fetch_buf() here * fetch_buf gets less than vhost_vq_num_batch_descs(vq); descriptors. ret = 1 * This loop calls again fetch_buf, but vq->ndescs > 0 (and avail_vq == last_avail_vq), so it just return 1 I think that we should check vq->ndescs == 0 instead of ndescs <= vhost_vq_num_batch_descs(vq). However, this could cause less descriptors to be fetches/cached, so less thoughput. Another possibility is to compare with vhost_vq_num_batch_descs(vq) for the "early return", or to find a sensible limit (increasing latency?). In my local version: diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 28f324fd77df..50b258a46cef 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -2310,12 +2310,7 @@ static int fetch_descs(struct vhost_virtqueue *vq) vq->ndescs = 0; } - if (vq->ndescs) - return 1; - - for (ret = 1; - ret > 0 && vq->ndescs <= vhost_vq_num_batch_descs(vq); - ret = fetch_buf(vq)) + for (ret = 1; ret > 0 && vq->ndescs == 0; ret = fetch_buf(vq)) ; /* On success we expect some descs */ --- > + > + /* On success we expect some descs */ > + BUG_ON(ret > 0 && !vq->ndescs); > + return ret; > +} > + > +/* Reverse the effects of fetch_descs */ > +static void unfetch_descs(struct vhost_virtqueue *vq) > +{ > + int i; > + > + for (i = vq->first_desc; i < vq->ndescs; ++i) > + if (!(vq->descs[i].flags & VRING_DESC_F_NEXT)) > + vq->last_avail_idx -= 1; > + vq->ndescs = 0; > +} > + > /* This looks in the virtqueue and for the first available buffer, and converts > * it to an iovec for convenient access. Since descriptors consist of some > * number of output then some number of input descriptors, it's actually two > @@ -2540,7 +2342,7 @@ static int fetch_descs(struct vhost_virtqueue *vq) > * This function returns the descriptor number found, or vq->num (which is > * never a valid descriptor number) if none was found. A negative code is > * returned on error. */ > -int vhost_get_vq_desc_batch(struct vhost_virtqueue *vq, > +int vhost_get_vq_desc(struct vhost_virtqueue *vq, > struct iovec iov[], unsigned int iov_size, > unsigned int *out_num, unsigned int *in_num, > struct vhost_log *log, unsigned int *log_num) > @@ -2549,7 +2351,7 @@ int vhost_get_vq_desc_batch(struct vhost_virtqueue *vq, > int i; > > if (ret <= 0) > - goto err_fetch; > + goto err; > > /* Now convert to IOV */ > /* When we start there are none of either input nor output. */ > @@ -2557,7 +2359,7 @@ int vhost_get_vq_desc_batch(struct vhost_virtqueue *vq, > if (unlikely(log)) > *log_num = 0; > > - for (i = 0; i < vq->ndescs; ++i) { > + for (i = vq->first_desc; i < vq->ndescs; ++i) { > unsigned iov_count = *in_num + *out_num; > struct vhost_desc *desc = &vq->descs[i]; > int access; > @@ -2603,24 +2405,26 @@ int vhost_get_vq_desc_batch(struct vhost_virtqueue *vq, > } > > ret = desc->id; > + > + if (!(desc->flags & VRING_DESC_F_NEXT)) > + break; > } > > - vq->ndescs = 0; > + vq->first_desc = i + 1; > > return ret; > > err: > - vhost_discard_vq_desc(vq, 1); > -err_fetch: > - vq->ndescs = 0; > + unfetch_descs(vq); > > return ret ? ret : vq->num; > } > -EXPORT_SYMBOL_GPL(vhost_get_vq_desc_batch); > +EXPORT_SYMBOL_GPL(vhost_get_vq_desc); > > /* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */ > void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n) > { > + unfetch_descs(vq); > vq->last_avail_idx -= n; > } > EXPORT_SYMBOL_GPL(vhost_discard_vq_desc); > diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h > index 87089d51490d..fed36af5c444 100644 > --- a/drivers/vhost/vhost.h > +++ b/drivers/vhost/vhost.h > @@ -81,6 +81,7 @@ struct vhost_virtqueue { > > struct vhost_desc *descs; > int ndescs; > + int first_desc; > int max_descs; > > struct file *kick; > @@ -189,10 +190,6 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg > bool vhost_vq_access_ok(struct vhost_virtqueue *vq); > bool vhost_log_access_ok(struct vhost_dev *); > > -int vhost_get_vq_desc_batch(struct vhost_virtqueue *, > - struct iovec iov[], unsigned int iov_count, > - unsigned int *out_num, unsigned int *in_num, > - struct vhost_log *log, unsigned int *log_num); > int vhost_get_vq_desc(struct vhost_virtqueue *, > struct iovec iov[], unsigned int iov_count, > unsigned int *out_num, unsigned int *in_num, > @@ -261,6 +258,8 @@ static inline void vhost_vq_set_backend(struct vhost_virtqueue *vq, > void *private_data) > { > vq->private_data = private_data; > + vq->ndescs = 0; > + vq->first_desc = 0; > } > > /** > -- > MST >
On Wed, 2020-06-10 at 07:36 -0400, Michael S. Tsirkin wrote: > As testing shows no performance change, switch to that now. > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > Signed-off-by: Eugenio Pérez <eperezma@redhat.com> > Link: https://lore.kernel.org/r/20200401183118.8334-3-eperezma@redhat.com > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > --- > drivers/vhost/test.c | 2 +- > drivers/vhost/vhost.c | 318 ++++++++---------------------------------- > drivers/vhost/vhost.h | 7 +- > 3 files changed, 65 insertions(+), 262 deletions(-) > > diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c > index 0466921f4772..7d69778aaa26 100644 > --- a/drivers/vhost/test.c > +++ b/drivers/vhost/test.c > @@ -119,7 +119,7 @@ static int vhost_test_open(struct inode *inode, struct file *f) > dev = &n->dev; > vqs[VHOST_TEST_VQ] = &n->vqs[VHOST_TEST_VQ]; > n->vqs[VHOST_TEST_VQ].handle_kick = handle_vq_kick; > - vhost_dev_init(dev, vqs, VHOST_TEST_VQ_MAX, UIO_MAXIOV, > + vhost_dev_init(dev, vqs, VHOST_TEST_VQ_MAX, UIO_MAXIOV + 64, > VHOST_TEST_PKT_WEIGHT, VHOST_TEST_WEIGHT, true, NULL); > > f->private_data = n; > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > index 11433d709651..28f324fd77df 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -304,6 +304,7 @@ static void vhost_vq_reset(struct vhost_dev *dev, > { > vq->num = 1; > vq->ndescs = 0; > + vq->first_desc = 0; > vq->desc = NULL; > vq->avail = NULL; > vq->used = NULL; > @@ -372,6 +373,11 @@ static int vhost_worker(void *data) > return 0; > } > > +static int vhost_vq_num_batch_descs(struct vhost_virtqueue *vq) > +{ > + return vq->max_descs - UIO_MAXIOV; > +} > + > static void vhost_vq_free_iovecs(struct vhost_virtqueue *vq) > { > kfree(vq->descs); > @@ -394,6 +400,9 @@ static long vhost_dev_alloc_iovecs(struct vhost_dev *dev) > for (i = 0; i < dev->nvqs; ++i) { > vq = dev->vqs[i]; > vq->max_descs = dev->iov_limit; > + if (vhost_vq_num_batch_descs(vq) < 0) { > + return -EINVAL; > + } > vq->descs = kmalloc_array(vq->max_descs, > sizeof(*vq->descs), > GFP_KERNEL); > @@ -1610,6 +1619,7 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg > vq->last_avail_idx = s.num; > /* Forget the cached index value. */ > vq->avail_idx = vq->last_avail_idx; > + vq->ndescs = vq->first_desc = 0; This is not needed if it is done in vhost_vq_set_backend, as far as I can tell. Actually, maybe it is even better to move `vq->avail_idx = vq->last_avail_idx;` line to vhost_vq_set_backend, it is part of the backend "set up" procedure, isn't it? I tested with virtio_test + batch tests sent in https://lkml.kernel.org/lkml/20200418102217.32327-1-eperezma@redhat.com/T/. I append here what I'm proposing in case it is clearer this way. Thanks! diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 4d198994e7be..809ad2cd2879 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -1617,9 +1617,6 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg break; } vq->last_avail_idx = s.num; - /* Forget the cached index value. */ - vq->avail_idx = vq->last_avail_idx; - vq->ndescs = vq->first_desc = 0; break; case VHOST_GET_VRING_BASE: s.index = idx; diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h index fed36af5c444..f4902dc808e4 100644 --- a/drivers/vhost/vhost.h +++ b/drivers/vhost/vhost.h @@ -258,6 +258,7 @@ static inline void vhost_vq_set_backend(struct vhost_virtqueue *vq, void *private_data) { vq->private_data = private_data; + vq->avail_idx = vq->last_avail_idx; vq->ndescs = 0; vq->first_desc = 0; } > break; > case VHOST_GET_VRING_BASE: > s.index = idx; > @@ -2078,253 +2088,6 @@ static unsigned next_desc(struct vhost_virtqueue *vq, struct vring_desc *desc) > return next; > } > > -static int get_indirect(struct vhost_virtqueue *vq, > - struct iovec iov[], unsigned int iov_size, > - unsigned int *out_num, unsigned int *in_num, > - struct vhost_log *log, unsigned int *log_num, > - struct vring_desc *indirect) > -{ > - struct vring_desc desc; > - unsigned int i = 0, count, found = 0; > - u32 len = vhost32_to_cpu(vq, indirect->len); > - struct iov_iter from; > - int ret, access; > - > - /* Sanity check */ > - if (unlikely(len % sizeof desc)) { > - vq_err(vq, "Invalid length in indirect descriptor: " > - "len 0x%llx not multiple of 0x%zx\n", > - (unsigned long long)len, > - sizeof desc); > - return -EINVAL; > - } > - > - ret = translate_desc(vq, vhost64_to_cpu(vq, indirect->addr), len, vq->indirect, > - UIO_MAXIOV, VHOST_ACCESS_RO); > - if (unlikely(ret < 0)) { > - if (ret != -EAGAIN) > - vq_err(vq, "Translation failure %d in indirect.\n", ret); > - return ret; > - } > - iov_iter_init(&from, READ, vq->indirect, ret, len); > - > - /* We will use the result as an address to read from, so most > - * architectures only need a compiler barrier here. */ > - read_barrier_depends(); > - > - count = len / sizeof desc; > - /* Buffers are chained via a 16 bit next field, so > - * we can have at most 2^16 of these. */ > - if (unlikely(count > USHRT_MAX + 1)) { > - vq_err(vq, "Indirect buffer length too big: %d\n", > - indirect->len); > - return -E2BIG; > - } > - > - do { > - unsigned iov_count = *in_num + *out_num; > - if (unlikely(++found > count)) { > - vq_err(vq, "Loop detected: last one at %u " > - "indirect size %u\n", > - i, count); > - return -EINVAL; > - } > - if (unlikely(!copy_from_iter_full(&desc, sizeof(desc), &from))) { > - vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n", > - i, (size_t)vhost64_to_cpu(vq, indirect->addr) + i * sizeof desc); > - return -EINVAL; > - } > - if (unlikely(desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_INDIRECT))) { > - vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n", > - i, (size_t)vhost64_to_cpu(vq, indirect->addr) + i * sizeof desc); > - return -EINVAL; > - } > - > - if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_WRITE)) > - access = VHOST_ACCESS_WO; > - else > - access = VHOST_ACCESS_RO; > - > - ret = translate_desc(vq, vhost64_to_cpu(vq, desc.addr), > - vhost32_to_cpu(vq, desc.len), iov + iov_count, > - iov_size - iov_count, access); > - if (unlikely(ret < 0)) { > - if (ret != -EAGAIN) > - vq_err(vq, "Translation failure %d indirect idx %d\n", > - ret, i); > - return ret; > - } > - /* If this is an input descriptor, increment that count. */ > - if (access == VHOST_ACCESS_WO) { > - *in_num += ret; > - if (unlikely(log && ret)) { > - log[*log_num].addr = vhost64_to_cpu(vq, desc.addr); > - log[*log_num].len = vhost32_to_cpu(vq, desc.len); > - ++*log_num; > - } > - } else { > - /* If it's an output descriptor, they're all supposed > - * to come before any input descriptors. */ > - if (unlikely(*in_num)) { > - vq_err(vq, "Indirect descriptor " > - "has out after in: idx %d\n", i); > - return -EINVAL; > - } > - *out_num += ret; > - } > - } while ((i = next_desc(vq, &desc)) != -1); > - return 0; > -} > - > -/* This looks in the virtqueue and for the first available buffer, and converts > - * it to an iovec for convenient access. Since descriptors consist of some > - * number of output then some number of input descriptors, it's actually two > - * iovecs, but we pack them into one and note how many of each there were. > - * > - * This function returns the descriptor number found, or vq->num (which is > - * never a valid descriptor number) if none was found. A negative code is > - * returned on error. */ > -int vhost_get_vq_desc(struct vhost_virtqueue *vq, > - struct iovec iov[], unsigned int iov_size, > - unsigned int *out_num, unsigned int *in_num, > - struct vhost_log *log, unsigned int *log_num) > -{ > - struct vring_desc desc; > - unsigned int i, head, found = 0; > - u16 last_avail_idx; > - __virtio16 avail_idx; > - __virtio16 ring_head; > - int ret, access; > - > - /* Check it isn't doing very strange things with descriptor numbers. */ > - last_avail_idx = vq->last_avail_idx; > - > - if (vq->avail_idx == vq->last_avail_idx) { > - if (unlikely(vhost_get_avail_idx(vq, &avail_idx))) { > - vq_err(vq, "Failed to access avail idx at %p\n", > - &vq->avail->idx); > - return -EFAULT; > - } > - vq->avail_idx = vhost16_to_cpu(vq, avail_idx); > - > - if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) { > - vq_err(vq, "Guest moved used index from %u to %u", > - last_avail_idx, vq->avail_idx); > - return -EFAULT; > - } > - > - /* If there's nothing new since last we looked, return > - * invalid. > - */ > - if (vq->avail_idx == last_avail_idx) > - return vq->num; > - > - /* Only get avail ring entries after they have been > - * exposed by guest. > - */ > - smp_rmb(); > - } > - > - /* Grab the next descriptor number they're advertising, and increment > - * the index we've seen. */ > - if (unlikely(vhost_get_avail_head(vq, &ring_head, last_avail_idx))) { > - vq_err(vq, "Failed to read head: idx %d address %p\n", > - last_avail_idx, > - &vq->avail->ring[last_avail_idx % vq->num]); > - return -EFAULT; > - } > - > - head = vhost16_to_cpu(vq, ring_head); > - > - /* If their number is silly, that's an error. */ > - if (unlikely(head >= vq->num)) { > - vq_err(vq, "Guest says index %u > %u is available", > - head, vq->num); > - return -EINVAL; > - } > - > - /* When we start there are none of either input nor output. */ > - *out_num = *in_num = 0; > - if (unlikely(log)) > - *log_num = 0; > - > - i = head; > - do { > - unsigned iov_count = *in_num + *out_num; > - if (unlikely(i >= vq->num)) { > - vq_err(vq, "Desc index is %u > %u, head = %u", > - i, vq->num, head); > - return -EINVAL; > - } > - if (unlikely(++found > vq->num)) { > - vq_err(vq, "Loop detected: last one at %u " > - "vq size %u head %u\n", > - i, vq->num, head); > - return -EINVAL; > - } > - ret = vhost_get_desc(vq, &desc, i); > - if (unlikely(ret)) { > - vq_err(vq, "Failed to get descriptor: idx %d addr %p\n", > - i, vq->desc + i); > - return -EFAULT; > - } > - if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_INDIRECT)) { > - ret = get_indirect(vq, iov, iov_size, > - out_num, in_num, > - log, log_num, &desc); > - if (unlikely(ret < 0)) { > - if (ret != -EAGAIN) > - vq_err(vq, "Failure detected " > - "in indirect descriptor at idx %d\n", i); > - return ret; > - } > - continue; > - } > - > - if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_WRITE)) > - access = VHOST_ACCESS_WO; > - else > - access = VHOST_ACCESS_RO; > - ret = translate_desc(vq, vhost64_to_cpu(vq, desc.addr), > - vhost32_to_cpu(vq, desc.len), iov + iov_count, > - iov_size - iov_count, access); > - if (unlikely(ret < 0)) { > - if (ret != -EAGAIN) > - vq_err(vq, "Translation failure %d descriptor idx %d\n", > - ret, i); > - return ret; > - } > - if (access == VHOST_ACCESS_WO) { > - /* If this is an input descriptor, > - * increment that count. */ > - *in_num += ret; > - if (unlikely(log && ret)) { > - log[*log_num].addr = vhost64_to_cpu(vq, desc.addr); > - log[*log_num].len = vhost32_to_cpu(vq, desc.len); > - ++*log_num; > - } > - } else { > - /* If it's an output descriptor, they're all supposed > - * to come before any input descriptors. */ > - if (unlikely(*in_num)) { > - vq_err(vq, "Descriptor has out after in: " > - "idx %d\n", i); > - return -EINVAL; > - } > - *out_num += ret; > - } > - } while ((i = next_desc(vq, &desc)) != -1); > - > - /* On success, increment avail index. */ > - vq->last_avail_idx++; > - > - /* Assume notifications from guest are disabled at this point, > - * if they aren't we would need to update avail_event index. */ > - BUG_ON(!(vq->used_flags & VRING_USED_F_NO_NOTIFY)); > - return head; > -} > -EXPORT_SYMBOL_GPL(vhost_get_vq_desc); > - > static struct vhost_desc *peek_split_desc(struct vhost_virtqueue *vq) > { > BUG_ON(!vq->ndescs); > @@ -2428,7 +2191,7 @@ static int fetch_indirect_descs(struct vhost_virtqueue *vq, > > /* This function returns a value > 0 if a descriptor was found, or 0 if none were found. > * A negative code is returned on error. */ > -static int fetch_descs(struct vhost_virtqueue *vq) > +static int fetch_buf(struct vhost_virtqueue *vq) > { > unsigned int i, head, found = 0; > struct vhost_desc *last; > @@ -2441,7 +2204,11 @@ static int fetch_descs(struct vhost_virtqueue *vq) > /* Check it isn't doing very strange things with descriptor numbers. */ > last_avail_idx = vq->last_avail_idx; > > - if (vq->avail_idx == vq->last_avail_idx) { > + if (unlikely(vq->avail_idx == vq->last_avail_idx)) { > + /* If we already have work to do, don't bother re-checking. */ > + if (likely(vq->ndescs)) > + return 1; > + > if (unlikely(vhost_get_avail_idx(vq, &avail_idx))) { > vq_err(vq, "Failed to access avail idx at %p\n", > &vq->avail->idx); > @@ -2532,6 +2299,41 @@ static int fetch_descs(struct vhost_virtqueue *vq) > return 1; > } > > +/* This function returns a value > 0 if a descriptor was found, or 0 if none were found. > + * A negative code is returned on error. */ > +static int fetch_descs(struct vhost_virtqueue *vq) > +{ > + int ret; > + > + if (unlikely(vq->first_desc >= vq->ndescs)) { > + vq->first_desc = 0; > + vq->ndescs = 0; > + } > + > + if (vq->ndescs) > + return 1; > + > + for (ret = 1; > + ret > 0 && vq->ndescs <= vhost_vq_num_batch_descs(vq); > + ret = fetch_buf(vq)) > + ; > + > + /* On success we expect some descs */ > + BUG_ON(ret > 0 && !vq->ndescs); > + return ret; > +} > + > +/* Reverse the effects of fetch_descs */ > +static void unfetch_descs(struct vhost_virtqueue *vq) > +{ > + int i; > + > + for (i = vq->first_desc; i < vq->ndescs; ++i) > + if (!(vq->descs[i].flags & VRING_DESC_F_NEXT)) > + vq->last_avail_idx -= 1; > + vq->ndescs = 0; > +} > + > /* This looks in the virtqueue and for the first available buffer, and converts > * it to an iovec for convenient access. Since descriptors consist of some > * number of output then some number of input descriptors, it's actually two > @@ -2540,7 +2342,7 @@ static int fetch_descs(struct vhost_virtqueue *vq) > * This function returns the descriptor number found, or vq->num (which is > * never a valid descriptor number) if none was found. A negative code is > * returned on error. */ > -int vhost_get_vq_desc_batch(struct vhost_virtqueue *vq, > +int vhost_get_vq_desc(struct vhost_virtqueue *vq, > struct iovec iov[], unsigned int iov_size, > unsigned int *out_num, unsigned int *in_num, > struct vhost_log *log, unsigned int *log_num) > @@ -2549,7 +2351,7 @@ int vhost_get_vq_desc_batch(struct vhost_virtqueue *vq, > int i; > > if (ret <= 0) > - goto err_fetch; > + goto err; > > /* Now convert to IOV */ > /* When we start there are none of either input nor output. */ > @@ -2557,7 +2359,7 @@ int vhost_get_vq_desc_batch(struct vhost_virtqueue *vq, > if (unlikely(log)) > *log_num = 0; > > - for (i = 0; i < vq->ndescs; ++i) { > + for (i = vq->first_desc; i < vq->ndescs; ++i) { > unsigned iov_count = *in_num + *out_num; > struct vhost_desc *desc = &vq->descs[i]; > int access; > @@ -2603,24 +2405,26 @@ int vhost_get_vq_desc_batch(struct vhost_virtqueue *vq, > } > > ret = desc->id; > + > + if (!(desc->flags & VRING_DESC_F_NEXT)) > + break; > } > > - vq->ndescs = 0; > + vq->first_desc = i + 1; > > return ret; > > err: > - vhost_discard_vq_desc(vq, 1); > -err_fetch: > - vq->ndescs = 0; > + unfetch_descs(vq); > > return ret ? ret : vq->num; > } > -EXPORT_SYMBOL_GPL(vhost_get_vq_desc_batch); > +EXPORT_SYMBOL_GPL(vhost_get_vq_desc); > > /* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */ > void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n) > { > + unfetch_descs(vq); > vq->last_avail_idx -= n; > } > EXPORT_SYMBOL_GPL(vhost_discard_vq_desc); > diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h > index 87089d51490d..fed36af5c444 100644 > --- a/drivers/vhost/vhost.h > +++ b/drivers/vhost/vhost.h > @@ -81,6 +81,7 @@ struct vhost_virtqueue { > > struct vhost_desc *descs; > int ndescs; > + int first_desc; > int max_descs; > > struct file *kick; > @@ -189,10 +190,6 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg > bool vhost_vq_access_ok(struct vhost_virtqueue *vq); > bool vhost_log_access_ok(struct vhost_dev *); > > -int vhost_get_vq_desc_batch(struct vhost_virtqueue *, > - struct iovec iov[], unsigned int iov_count, > - unsigned int *out_num, unsigned int *in_num, > - struct vhost_log *log, unsigned int *log_num); > int vhost_get_vq_desc(struct vhost_virtqueue *, > struct iovec iov[], unsigned int iov_count, > unsigned int *out_num, unsigned int *in_num, > @@ -261,6 +258,8 @@ static inline void vhost_vq_set_backend(struct vhost_virtqueue *vq, > void *private_data) > { > vq->private_data = private_data; > + vq->ndescs = 0; > + vq->first_desc = 0; > } > > /**
On Wed, Jun 10, 2020 at 04:29:29PM +0200, Eugenio Pérez wrote: > On Wed, 2020-06-10 at 07:36 -0400, Michael S. Tsirkin wrote: > > As testing shows no performance change, switch to that now. > > > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > > Signed-off-by: Eugenio Pérez <eperezma@redhat.com> > > Link: https://lore.kernel.org/r/20200401183118.8334-3-eperezma@redhat.com > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > > --- > > drivers/vhost/test.c | 2 +- > > drivers/vhost/vhost.c | 318 ++++++++---------------------------------- > > drivers/vhost/vhost.h | 7 +- > > 3 files changed, 65 insertions(+), 262 deletions(-) > > > > diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c > > index 0466921f4772..7d69778aaa26 100644 > > --- a/drivers/vhost/test.c > > +++ b/drivers/vhost/test.c > > @@ -119,7 +119,7 @@ static int vhost_test_open(struct inode *inode, struct file *f) > > dev = &n->dev; > > vqs[VHOST_TEST_VQ] = &n->vqs[VHOST_TEST_VQ]; > > n->vqs[VHOST_TEST_VQ].handle_kick = handle_vq_kick; > > - vhost_dev_init(dev, vqs, VHOST_TEST_VQ_MAX, UIO_MAXIOV, > > + vhost_dev_init(dev, vqs, VHOST_TEST_VQ_MAX, UIO_MAXIOV + 64, > > VHOST_TEST_PKT_WEIGHT, VHOST_TEST_WEIGHT, true, NULL); > > > > f->private_data = n; > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > > index 11433d709651..28f324fd77df 100644 > > --- a/drivers/vhost/vhost.c > > +++ b/drivers/vhost/vhost.c > > @@ -304,6 +304,7 @@ static void vhost_vq_reset(struct vhost_dev *dev, > > { > > vq->num = 1; > > vq->ndescs = 0; > > + vq->first_desc = 0; > > vq->desc = NULL; > > vq->avail = NULL; > > vq->used = NULL; > > @@ -372,6 +373,11 @@ static int vhost_worker(void *data) > > return 0; > > } > > > > +static int vhost_vq_num_batch_descs(struct vhost_virtqueue *vq) > > +{ > > + return vq->max_descs - UIO_MAXIOV; > > +} > > + > > static void vhost_vq_free_iovecs(struct vhost_virtqueue *vq) > > { > > kfree(vq->descs); > > @@ -394,6 +400,9 @@ static long vhost_dev_alloc_iovecs(struct vhost_dev *dev) > > for (i = 0; i < dev->nvqs; ++i) { > > vq = dev->vqs[i]; > > vq->max_descs = dev->iov_limit; > > + if (vhost_vq_num_batch_descs(vq) < 0) { > > + return -EINVAL; > > + } > > vq->descs = kmalloc_array(vq->max_descs, > > sizeof(*vq->descs), > > GFP_KERNEL); > > @@ -1610,6 +1619,7 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg > > vq->last_avail_idx = s.num; > > /* Forget the cached index value. */ > > vq->avail_idx = vq->last_avail_idx; > > + vq->ndescs = vq->first_desc = 0; > > This is not needed if it is done in vhost_vq_set_backend, as far as I can tell. > > Actually, maybe it is even better to move `vq->avail_idx = vq->last_avail_idx;` line to vhost_vq_set_backend, it is part > of the backend "set up" procedure, isn't it? > > I tested with virtio_test + batch tests sent in > https://lkml.kernel.org/lkml/20200418102217.32327-1-eperezma@redhat.com/T/. Ow did I forget to merge them for rc1? Should I have? Maybe Linus won't yell to hard at me if I merge them after rc1. > I append here what I'm proposing in case it is clearer this way. > > Thanks! > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > index 4d198994e7be..809ad2cd2879 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -1617,9 +1617,6 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg > break; > } > vq->last_avail_idx = s.num; > - /* Forget the cached index value. */ > - vq->avail_idx = vq->last_avail_idx; > - vq->ndescs = vq->first_desc = 0; > break; > case VHOST_GET_VRING_BASE: > s.index = idx; > diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h > index fed36af5c444..f4902dc808e4 100644 > --- a/drivers/vhost/vhost.h > +++ b/drivers/vhost/vhost.h > @@ -258,6 +258,7 @@ static inline void vhost_vq_set_backend(struct vhost_virtqueue *vq, > void *private_data) > { > vq->private_data = private_data; > + vq->avail_idx = vq->last_avail_idx; > vq->ndescs = 0; > vq->first_desc = 0; > } > Seems like a nice cleanup, though it's harmless right?
On Wed, Jun 10, 2020 at 5:08 PM Michael S. Tsirkin <mst@redhat.com> wrote: > > On Wed, Jun 10, 2020 at 04:29:29PM +0200, Eugenio Pérez wrote: > > On Wed, 2020-06-10 at 07:36 -0400, Michael S. Tsirkin wrote: > > > As testing shows no performance change, switch to that now. > > > > > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > > > Signed-off-by: Eugenio Pérez <eperezma@redhat.com> > > > Link: https://lore.kernel.org/r/20200401183118.8334-3-eperezma@redhat.com > > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > > > --- > > > drivers/vhost/test.c | 2 +- > > > drivers/vhost/vhost.c | 318 ++++++++---------------------------------- > > > drivers/vhost/vhost.h | 7 +- > > > 3 files changed, 65 insertions(+), 262 deletions(-) > > > > > > diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c > > > index 0466921f4772..7d69778aaa26 100644 > > > --- a/drivers/vhost/test.c > > > +++ b/drivers/vhost/test.c > > > @@ -119,7 +119,7 @@ static int vhost_test_open(struct inode *inode, struct file *f) > > > dev = &n->dev; > > > vqs[VHOST_TEST_VQ] = &n->vqs[VHOST_TEST_VQ]; > > > n->vqs[VHOST_TEST_VQ].handle_kick = handle_vq_kick; > > > - vhost_dev_init(dev, vqs, VHOST_TEST_VQ_MAX, UIO_MAXIOV, > > > + vhost_dev_init(dev, vqs, VHOST_TEST_VQ_MAX, UIO_MAXIOV + 64, > > > VHOST_TEST_PKT_WEIGHT, VHOST_TEST_WEIGHT, true, NULL); > > > > > > f->private_data = n; > > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > > > index 11433d709651..28f324fd77df 100644 > > > --- a/drivers/vhost/vhost.c > > > +++ b/drivers/vhost/vhost.c > > > @@ -304,6 +304,7 @@ static void vhost_vq_reset(struct vhost_dev *dev, > > > { > > > vq->num = 1; > > > vq->ndescs = 0; > > > + vq->first_desc = 0; > > > vq->desc = NULL; > > > vq->avail = NULL; > > > vq->used = NULL; > > > @@ -372,6 +373,11 @@ static int vhost_worker(void *data) > > > return 0; > > > } > > > > > > +static int vhost_vq_num_batch_descs(struct vhost_virtqueue *vq) > > > +{ > > > + return vq->max_descs - UIO_MAXIOV; > > > +} > > > + > > > static void vhost_vq_free_iovecs(struct vhost_virtqueue *vq) > > > { > > > kfree(vq->descs); > > > @@ -394,6 +400,9 @@ static long vhost_dev_alloc_iovecs(struct vhost_dev *dev) > > > for (i = 0; i < dev->nvqs; ++i) { > > > vq = dev->vqs[i]; > > > vq->max_descs = dev->iov_limit; > > > + if (vhost_vq_num_batch_descs(vq) < 0) { > > > + return -EINVAL; > > > + } > > > vq->descs = kmalloc_array(vq->max_descs, > > > sizeof(*vq->descs), > > > GFP_KERNEL); > > > @@ -1610,6 +1619,7 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg > > > vq->last_avail_idx = s.num; > > > /* Forget the cached index value. */ > > > vq->avail_idx = vq->last_avail_idx; > > > + vq->ndescs = vq->first_desc = 0; > > > > This is not needed if it is done in vhost_vq_set_backend, as far as I can tell. > > > > Actually, maybe it is even better to move `vq->avail_idx = vq->last_avail_idx;` line to vhost_vq_set_backend, it is part > > of the backend "set up" procedure, isn't it? > > > > I tested with virtio_test + batch tests sent in > > https://lkml.kernel.org/lkml/20200418102217.32327-1-eperezma@redhat.com/T/. > > Ow did I forget to merge them for rc1? Should I have? Maybe Linus won't > yell to hard at me if I merge them after rc1. > > > > I append here what I'm proposing in case it is clearer this way. > > > > Thanks! > > > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > > index 4d198994e7be..809ad2cd2879 100644 > > --- a/drivers/vhost/vhost.c > > +++ b/drivers/vhost/vhost.c > > @@ -1617,9 +1617,6 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg > > break; > > } > > vq->last_avail_idx = s.num; > > - /* Forget the cached index value. */ > > - vq->avail_idx = vq->last_avail_idx; > > - vq->ndescs = vq->first_desc = 0; > > break; > > case VHOST_GET_VRING_BASE: > > s.index = idx; > > diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h > > index fed36af5c444..f4902dc808e4 100644 > > --- a/drivers/vhost/vhost.h > > +++ b/drivers/vhost/vhost.h > > @@ -258,6 +258,7 @@ static inline void vhost_vq_set_backend(struct vhost_virtqueue *vq, > > void *private_data) > > { > > vq->private_data = private_data; > > + vq->avail_idx = vq->last_avail_idx; > > vq->ndescs = 0; > > vq->first_desc = 0; > > } > > > > Seems like a nice cleanup, though it's harmless right? > Fields ndescs and first_descs are supposed to be updated outside, that was the intention but maybe I forgot to delete it here, not sure. Regarding avail_idx, the whole change has been tested with vhost_test and for vhost needs to have a backend to modify it already so it seems safe to me.
On Wed, Jun 10, 2020 at 02:37:50PM +0200, Eugenio Perez Martin wrote: > > +/* This function returns a value > 0 if a descriptor was found, or 0 if none were found. > > + * A negative code is returned on error. */ > > +static int fetch_descs(struct vhost_virtqueue *vq) > > +{ > > + int ret; > > + > > + if (unlikely(vq->first_desc >= vq->ndescs)) { > > + vq->first_desc = 0; > > + vq->ndescs = 0; > > + } > > + > > + if (vq->ndescs) > > + return 1; > > + > > + for (ret = 1; > > + ret > 0 && vq->ndescs <= vhost_vq_num_batch_descs(vq); > > + ret = fetch_buf(vq)) > > + ; > > (Expanding comment in V6): > > We get an infinite loop this way: > * vq->ndescs == 0, so we call fetch_buf() here > * fetch_buf gets less than vhost_vq_num_batch_descs(vq); descriptors. ret = 1 > * This loop calls again fetch_buf, but vq->ndescs > 0 (and avail_vq == > last_avail_vq), so it just return 1 That's what [PATCH RFC v7 08/14] fixup! vhost: use batched get_vq_desc version is supposed to fix.
On Wed, Jun 10, 2020 at 5:13 PM Michael S. Tsirkin <mst@redhat.com> wrote: > > On Wed, Jun 10, 2020 at 02:37:50PM +0200, Eugenio Perez Martin wrote: > > > +/* This function returns a value > 0 if a descriptor was found, or 0 if none were found. > > > + * A negative code is returned on error. */ > > > +static int fetch_descs(struct vhost_virtqueue *vq) > > > +{ > > > + int ret; > > > + > > > + if (unlikely(vq->first_desc >= vq->ndescs)) { > > > + vq->first_desc = 0; > > > + vq->ndescs = 0; > > > + } > > > + > > > + if (vq->ndescs) > > > + return 1; > > > + > > > + for (ret = 1; > > > + ret > 0 && vq->ndescs <= vhost_vq_num_batch_descs(vq); > > > + ret = fetch_buf(vq)) > > > + ; > > > > (Expanding comment in V6): > > > > We get an infinite loop this way: > > * vq->ndescs == 0, so we call fetch_buf() here > > * fetch_buf gets less than vhost_vq_num_batch_descs(vq); descriptors. ret = 1 > > * This loop calls again fetch_buf, but vq->ndescs > 0 (and avail_vq == > > last_avail_vq), so it just return 1 > > That's what > [PATCH RFC v7 08/14] fixup! vhost: use batched get_vq_desc version > is supposed to fix. > Sorry, I forgot to include that fixup. With it I don't see CPU stalls, but with that version latency has increased a lot and I see packet lost: + ping -c 5 10.200.0.1 PING 10.200.0.1 (10.200.0.1) 56(84) bytes of data. From 10.200.0.2 icmp_seq=1 Destination Host Unreachable From 10.200.0.2 icmp_seq=2 Destination Host Unreachable From 10.200.0.2 icmp_seq=3 Destination Host Unreachable 64 bytes from 10.200.0.1: icmp_seq=5 ttl=64 time=6848 ms --- 10.200.0.1 ping statistics --- 5 packets transmitted, 1 received, +3 errors, 80% packet loss, time 76ms rtt min/avg/max/mdev = 6848.316/6848.316/6848.316/0.000 ms, pipe 4 -- I cannot even use netperf. If I modify with my proposed version: + ping -c 5 10.200.0.1 PING 10.200.0.1 (10.200.0.1) 56(84) bytes of data. 64 bytes from 10.200.0.1: icmp_seq=1 ttl=64 time=7.07 ms 64 bytes from 10.200.0.1: icmp_seq=2 ttl=64 time=0.358 ms 64 bytes from 10.200.0.1: icmp_seq=3 ttl=64 time=5.35 ms 64 bytes from 10.200.0.1: icmp_seq=4 ttl=64 time=2.27 ms 64 bytes from 10.200.0.1: icmp_seq=5 ttl=64 time=0.426 ms [root@localhost ~]# netperf -H 10.200.0.1 -p 12865 -l 10 -t TCP_STREAM MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 10.200.0.1 () port 0 AF_INET Recv Send Send Socket Socket Message Elapsed Size Size Size Time Throughput bytes bytes bytes secs. 10^6bits/sec 131072 16384 16384 10.01 4742.36 [root@localhost ~]# netperf -H 10.200.0.1 -p 12865 -l 10 -t UDP_STREAM MIGRATED UDP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 10.200.0.1 () port 0 AF_INET Socket Message Elapsed Messages Size Size Time Okay Errors Throughput bytes bytes secs # # 10^6bits/sec 212992 65507 10.00 9214 0 482.83 212992 10.00 9214 482.83 I will compare with the non-batch version for reference, but the difference between the two is noticeable. Maybe it's worth finding a good value for the if() inside fetch_buf? Thanks! > -- > MST >
On Wed, Jun 10, 2020 at 06:18:32PM +0200, Eugenio Perez Martin wrote: > On Wed, Jun 10, 2020 at 5:13 PM Michael S. Tsirkin <mst@redhat.com> wrote: > > > > On Wed, Jun 10, 2020 at 02:37:50PM +0200, Eugenio Perez Martin wrote: > > > > +/* This function returns a value > 0 if a descriptor was found, or 0 if none were found. > > > > + * A negative code is returned on error. */ > > > > +static int fetch_descs(struct vhost_virtqueue *vq) > > > > +{ > > > > + int ret; > > > > + > > > > + if (unlikely(vq->first_desc >= vq->ndescs)) { > > > > + vq->first_desc = 0; > > > > + vq->ndescs = 0; > > > > + } > > > > + > > > > + if (vq->ndescs) > > > > + return 1; > > > > + > > > > + for (ret = 1; > > > > + ret > 0 && vq->ndescs <= vhost_vq_num_batch_descs(vq); > > > > + ret = fetch_buf(vq)) > > > > + ; > > > > > > (Expanding comment in V6): > > > > > > We get an infinite loop this way: > > > * vq->ndescs == 0, so we call fetch_buf() here > > > * fetch_buf gets less than vhost_vq_num_batch_descs(vq); descriptors. ret = 1 > > > * This loop calls again fetch_buf, but vq->ndescs > 0 (and avail_vq == > > > last_avail_vq), so it just return 1 > > > > That's what > > [PATCH RFC v7 08/14] fixup! vhost: use batched get_vq_desc version > > is supposed to fix. > > > > Sorry, I forgot to include that fixup. > > With it I don't see CPU stalls, but with that version latency has > increased a lot and I see packet lost: > + ping -c 5 10.200.0.1 > PING 10.200.0.1 (10.200.0.1) 56(84) bytes of data. > >From 10.200.0.2 icmp_seq=1 Destination Host Unreachable > >From 10.200.0.2 icmp_seq=2 Destination Host Unreachable > >From 10.200.0.2 icmp_seq=3 Destination Host Unreachable > 64 bytes from 10.200.0.1: icmp_seq=5 ttl=64 time=6848 ms > > --- 10.200.0.1 ping statistics --- > 5 packets transmitted, 1 received, +3 errors, 80% packet loss, time 76ms > rtt min/avg/max/mdev = 6848.316/6848.316/6848.316/0.000 ms, pipe 4 > -- > > I cannot even use netperf. OK so that's the bug to try to find and fix I think. > If I modify with my proposed version: > + ping -c 5 10.200.0.1 > PING 10.200.0.1 (10.200.0.1) 56(84) bytes of data. > 64 bytes from 10.200.0.1: icmp_seq=1 ttl=64 time=7.07 ms > 64 bytes from 10.200.0.1: icmp_seq=2 ttl=64 time=0.358 ms > 64 bytes from 10.200.0.1: icmp_seq=3 ttl=64 time=5.35 ms > 64 bytes from 10.200.0.1: icmp_seq=4 ttl=64 time=2.27 ms > 64 bytes from 10.200.0.1: icmp_seq=5 ttl=64 time=0.426 ms Not sure which version this is. > [root@localhost ~]# netperf -H 10.200.0.1 -p 12865 -l 10 -t TCP_STREAM > MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to > 10.200.0.1 () port 0 AF_INET > Recv Send Send > Socket Socket Message Elapsed > Size Size Size Time Throughput > bytes bytes bytes secs. 10^6bits/sec > > 131072 16384 16384 10.01 4742.36 > [root@localhost ~]# netperf -H 10.200.0.1 -p 12865 -l 10 -t UDP_STREAM > MIGRATED UDP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to > 10.200.0.1 () port 0 AF_INET > Socket Message Elapsed Messages > Size Size Time Okay Errors Throughput > bytes bytes secs # # 10^6bits/sec > > 212992 65507 10.00 9214 0 482.83 > 212992 10.00 9214 482.83 > > I will compare with the non-batch version for reference, but the > difference between the two is noticeable. Maybe it's worth finding a > good value for the if() inside fetch_buf? > > Thanks! > I don't think it's performance, I think it's a bug somewhere, e.g. maybe we corrupt a packet, or stall the queue, or something like this. Let's do this, I will squash the fixups and post v8 so you can bisect and then debug cleanly. > > -- > > MST > >
On Thu, 2020-06-11 at 07:30 -0400, Michael S. Tsirkin wrote: > On Wed, Jun 10, 2020 at 06:18:32PM +0200, Eugenio Perez Martin wrote: > > On Wed, Jun 10, 2020 at 5:13 PM Michael S. Tsirkin <mst@redhat.com> wrote: > > > On Wed, Jun 10, 2020 at 02:37:50PM +0200, Eugenio Perez Martin wrote: > > > > > +/* This function returns a value > 0 if a descriptor was found, or 0 if none were found. > > > > > + * A negative code is returned on error. */ > > > > > +static int fetch_descs(struct vhost_virtqueue *vq) > > > > > +{ > > > > > + int ret; > > > > > + > > > > > + if (unlikely(vq->first_desc >= vq->ndescs)) { > > > > > + vq->first_desc = 0; > > > > > + vq->ndescs = 0; > > > > > + } > > > > > + > > > > > + if (vq->ndescs) > > > > > + return 1; > > > > > + > > > > > + for (ret = 1; > > > > > + ret > 0 && vq->ndescs <= vhost_vq_num_batch_descs(vq); > > > > > + ret = fetch_buf(vq)) > > > > > + ; > > > > > > > > (Expanding comment in V6): > > > > > > > > We get an infinite loop this way: > > > > * vq->ndescs == 0, so we call fetch_buf() here > > > > * fetch_buf gets less than vhost_vq_num_batch_descs(vq); descriptors. ret = 1 > > > > * This loop calls again fetch_buf, but vq->ndescs > 0 (and avail_vq == > > > > last_avail_vq), so it just return 1 > > > > > > That's what > > > [PATCH RFC v7 08/14] fixup! vhost: use batched get_vq_desc version > > > is supposed to fix. > > > > > > > Sorry, I forgot to include that fixup. > > > > With it I don't see CPU stalls, but with that version latency has > > increased a lot and I see packet lost: > > + ping -c 5 10.200.0.1 > > PING 10.200.0.1 (10.200.0.1) 56(84) bytes of data. > > > From 10.200.0.2 icmp_seq=1 Destination Host Unreachable > > > From 10.200.0.2 icmp_seq=2 Destination Host Unreachable > > > From 10.200.0.2 icmp_seq=3 Destination Host Unreachable > > 64 bytes from 10.200.0.1: icmp_seq=5 ttl=64 time=6848 ms > > > > --- 10.200.0.1 ping statistics --- > > 5 packets transmitted, 1 received, +3 errors, 80% packet loss, time 76ms > > rtt min/avg/max/mdev = 6848.316/6848.316/6848.316/0.000 ms, pipe 4 > > -- > > > > I cannot even use netperf. > > OK so that's the bug to try to find and fix I think. > > > > If I modify with my proposed version: > > + ping -c 5 10.200.0.1 > > PING 10.200.0.1 (10.200.0.1) 56(84) bytes of data. > > 64 bytes from 10.200.0.1: icmp_seq=1 ttl=64 time=7.07 ms > > 64 bytes from 10.200.0.1: icmp_seq=2 ttl=64 time=0.358 ms > > 64 bytes from 10.200.0.1: icmp_seq=3 ttl=64 time=5.35 ms > > 64 bytes from 10.200.0.1: icmp_seq=4 ttl=64 time=2.27 ms > > 64 bytes from 10.200.0.1: icmp_seq=5 ttl=64 time=0.426 ms > > Not sure which version this is. > > > [root@localhost ~]# netperf -H 10.200.0.1 -p 12865 -l 10 -t TCP_STREAM > > MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to > > 10.200.0.1 () port 0 AF_INET > > Recv Send Send > > Socket Socket Message Elapsed > > Size Size Size Time Throughput > > bytes bytes bytes secs. 10^6bits/sec > > > > 131072 16384 16384 10.01 4742.36 > > [root@localhost ~]# netperf -H 10.200.0.1 -p 12865 -l 10 -t UDP_STREAM > > MIGRATED UDP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to > > 10.200.0.1 () port 0 AF_INET > > Socket Message Elapsed Messages > > Size Size Time Okay Errors Throughput > > bytes bytes secs # # 10^6bits/sec > > > > 212992 65507 10.00 9214 0 482.83 > > 212992 10.00 9214 482.83 > > > > I will compare with the non-batch version for reference, but the > > difference between the two is noticeable. Maybe it's worth finding a > > good value for the if() inside fetch_buf? > > > > Thanks! > > > > I don't think it's performance, I think it's a bug somewhere, > e.g. maybe we corrupt a packet, or stall the queue, or > something like this. > > Let's do this, I will squash the fixups and post v8 so you can bisect > and then debug cleanly. Ok, so if we apply the patch proposed in v7 08/14 (Or the version 8 of the patchset sent), this is what happens: 1. Userland (virtio_test in my case) introduces just one buffer in vq, and it kicks 2. vhost module reaches fetch_descs, called from vhost_get_vq_desc. From there we call fetch_buf in a for loop. 3. The first time we call fetch_buf, it returns properly one buffer. However, the second time we call it, it returns 0 because vq->avail_idx == vq->last_avail_idx and vq->avail_idx == last_avail_idx code path. 4. fetch_descs assign ret = 0, so it returns 0. vhost_get_vq_desc will goto err, and it will signal no new buffer (returning vq->num). So to fix it and maintain the batching maybe we could return vq->ndescs in case ret == 0: diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index c0dfb5e3d2af..5993d4f34ca9 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -2315,7 +2327,8 @@ static int fetch_descs(struct vhost_virtqueue *vq) /* On success we expect some descs */ BUG_ON(ret > 0 && !vq->ndescs); - return ret; + return ret ?: vq->ndescs; } /* Reverse the effects of fetch_descs */ -- Another possibility could be to return different codes from fetch_buf, but I find the suggested modification easier. What do you think? Thanks!
On Mon, Jun 15, 2020 at 6:05 PM Eugenio Pérez <eperezma@redhat.com> wrote: > > On Thu, 2020-06-11 at 07:30 -0400, Michael S. Tsirkin wrote: > > On Wed, Jun 10, 2020 at 06:18:32PM +0200, Eugenio Perez Martin wrote: > > > On Wed, Jun 10, 2020 at 5:13 PM Michael S. Tsirkin <mst@redhat.com> wrote: > > > > On Wed, Jun 10, 2020 at 02:37:50PM +0200, Eugenio Perez Martin wrote: > > > > > > +/* This function returns a value > 0 if a descriptor was found, or 0 if none were found. > > > > > > + * A negative code is returned on error. */ > > > > > > +static int fetch_descs(struct vhost_virtqueue *vq) > > > > > > +{ > > > > > > + int ret; > > > > > > + > > > > > > + if (unlikely(vq->first_desc >= vq->ndescs)) { > > > > > > + vq->first_desc = 0; > > > > > > + vq->ndescs = 0; > > > > > > + } > > > > > > + > > > > > > + if (vq->ndescs) > > > > > > + return 1; > > > > > > + > > > > > > + for (ret = 1; > > > > > > + ret > 0 && vq->ndescs <= vhost_vq_num_batch_descs(vq); > > > > > > + ret = fetch_buf(vq)) > > > > > > + ; > > > > > > > > > > (Expanding comment in V6): > > > > > > > > > > We get an infinite loop this way: > > > > > * vq->ndescs == 0, so we call fetch_buf() here > > > > > * fetch_buf gets less than vhost_vq_num_batch_descs(vq); descriptors. ret = 1 > > > > > * This loop calls again fetch_buf, but vq->ndescs > 0 (and avail_vq == > > > > > last_avail_vq), so it just return 1 > > > > > > > > That's what > > > > [PATCH RFC v7 08/14] fixup! vhost: use batched get_vq_desc version > > > > is supposed to fix. > > > > > > > > > > Sorry, I forgot to include that fixup. > > > > > > With it I don't see CPU stalls, but with that version latency has > > > increased a lot and I see packet lost: > > > + ping -c 5 10.200.0.1 > > > PING 10.200.0.1 (10.200.0.1) 56(84) bytes of data. > > > > From 10.200.0.2 icmp_seq=1 Destination Host Unreachable > > > > From 10.200.0.2 icmp_seq=2 Destination Host Unreachable > > > > From 10.200.0.2 icmp_seq=3 Destination Host Unreachable > > > 64 bytes from 10.200.0.1: icmp_seq=5 ttl=64 time=6848 ms > > > > > > --- 10.200.0.1 ping statistics --- > > > 5 packets transmitted, 1 received, +3 errors, 80% packet loss, time 76ms > > > rtt min/avg/max/mdev = 6848.316/6848.316/6848.316/0.000 ms, pipe 4 > > > -- > > > > > > I cannot even use netperf. > > > > OK so that's the bug to try to find and fix I think. > > > > > > > If I modify with my proposed version: > > > + ping -c 5 10.200.0.1 > > > PING 10.200.0.1 (10.200.0.1) 56(84) bytes of data. > > > 64 bytes from 10.200.0.1: icmp_seq=1 ttl=64 time=7.07 ms > > > 64 bytes from 10.200.0.1: icmp_seq=2 ttl=64 time=0.358 ms > > > 64 bytes from 10.200.0.1: icmp_seq=3 ttl=64 time=5.35 ms > > > 64 bytes from 10.200.0.1: icmp_seq=4 ttl=64 time=2.27 ms > > > 64 bytes from 10.200.0.1: icmp_seq=5 ttl=64 time=0.426 ms > > > > Not sure which version this is. > > > > > [root@localhost ~]# netperf -H 10.200.0.1 -p 12865 -l 10 -t TCP_STREAM > > > MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to > > > 10.200.0.1 () port 0 AF_INET > > > Recv Send Send > > > Socket Socket Message Elapsed > > > Size Size Size Time Throughput > > > bytes bytes bytes secs. 10^6bits/sec > > > > > > 131072 16384 16384 10.01 4742.36 > > > [root@localhost ~]# netperf -H 10.200.0.1 -p 12865 -l 10 -t UDP_STREAM > > > MIGRATED UDP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to > > > 10.200.0.1 () port 0 AF_INET > > > Socket Message Elapsed Messages > > > Size Size Time Okay Errors Throughput > > > bytes bytes secs # # 10^6bits/sec > > > > > > 212992 65507 10.00 9214 0 482.83 > > > 212992 10.00 9214 482.83 > > > > > > I will compare with the non-batch version for reference, but the > > > difference between the two is noticeable. Maybe it's worth finding a > > > good value for the if() inside fetch_buf? > > > > > > Thanks! > > > > > > > I don't think it's performance, I think it's a bug somewhere, > > e.g. maybe we corrupt a packet, or stall the queue, or > > something like this. > > > > Let's do this, I will squash the fixups and post v8 so you can bisect > > and then debug cleanly. > > Ok, so if we apply the patch proposed in v7 08/14 (Or the version 8 of the patchset sent), this is what happens: > > 1. Userland (virtio_test in my case) introduces just one buffer in vq, and it kicks > 2. vhost module reaches fetch_descs, called from vhost_get_vq_desc. From there we call fetch_buf in a for loop. > 3. The first time we call fetch_buf, it returns properly one buffer. However, the second time we call it, it returns 0 > because vq->avail_idx == vq->last_avail_idx and vq->avail_idx == last_avail_idx code path. > 4. fetch_descs assign ret = 0, so it returns 0. vhost_get_vq_desc will goto err, and it will signal no new buffer > (returning vq->num). > > So to fix it and maintain the batching maybe we could return vq->ndescs in case ret == 0: > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > index c0dfb5e3d2af..5993d4f34ca9 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -2315,7 +2327,8 @@ static int fetch_descs(struct vhost_virtqueue *vq) > > /* On success we expect some descs */ > BUG_ON(ret > 0 && !vq->ndescs); > - return ret; > + return ret ?: vq->ndescs; > } > > /* Reverse the effects of fetch_descs */ > -- > > Another possibility could be to return different codes from fetch_buf, but I find the suggested modification easier. > > What do you think? > > Thanks! > Hi! I can send a proposed RFC v9 in case it is more convenient for you. Thanks!
On Tue, Jun 16, 2020 at 05:23:43PM +0200, Eugenio Perez Martin wrote: > On Mon, Jun 15, 2020 at 6:05 PM Eugenio Pérez <eperezma@redhat.com> wrote: > > > > On Thu, 2020-06-11 at 07:30 -0400, Michael S. Tsirkin wrote: > > > On Wed, Jun 10, 2020 at 06:18:32PM +0200, Eugenio Perez Martin wrote: > > > > On Wed, Jun 10, 2020 at 5:13 PM Michael S. Tsirkin <mst@redhat.com> wrote: > > > > > On Wed, Jun 10, 2020 at 02:37:50PM +0200, Eugenio Perez Martin wrote: > > > > > > > +/* This function returns a value > 0 if a descriptor was found, or 0 if none were found. > > > > > > > + * A negative code is returned on error. */ > > > > > > > +static int fetch_descs(struct vhost_virtqueue *vq) > > > > > > > +{ > > > > > > > + int ret; > > > > > > > + > > > > > > > + if (unlikely(vq->first_desc >= vq->ndescs)) { > > > > > > > + vq->first_desc = 0; > > > > > > > + vq->ndescs = 0; > > > > > > > + } > > > > > > > + > > > > > > > + if (vq->ndescs) > > > > > > > + return 1; > > > > > > > + > > > > > > > + for (ret = 1; > > > > > > > + ret > 0 && vq->ndescs <= vhost_vq_num_batch_descs(vq); > > > > > > > + ret = fetch_buf(vq)) > > > > > > > + ; > > > > > > > > > > > > (Expanding comment in V6): > > > > > > > > > > > > We get an infinite loop this way: > > > > > > * vq->ndescs == 0, so we call fetch_buf() here > > > > > > * fetch_buf gets less than vhost_vq_num_batch_descs(vq); descriptors. ret = 1 > > > > > > * This loop calls again fetch_buf, but vq->ndescs > 0 (and avail_vq == > > > > > > last_avail_vq), so it just return 1 > > > > > > > > > > That's what > > > > > [PATCH RFC v7 08/14] fixup! vhost: use batched get_vq_desc version > > > > > is supposed to fix. > > > > > > > > > > > > > Sorry, I forgot to include that fixup. > > > > > > > > With it I don't see CPU stalls, but with that version latency has > > > > increased a lot and I see packet lost: > > > > + ping -c 5 10.200.0.1 > > > > PING 10.200.0.1 (10.200.0.1) 56(84) bytes of data. > > > > > From 10.200.0.2 icmp_seq=1 Destination Host Unreachable > > > > > From 10.200.0.2 icmp_seq=2 Destination Host Unreachable > > > > > From 10.200.0.2 icmp_seq=3 Destination Host Unreachable > > > > 64 bytes from 10.200.0.1: icmp_seq=5 ttl=64 time=6848 ms > > > > > > > > --- 10.200.0.1 ping statistics --- > > > > 5 packets transmitted, 1 received, +3 errors, 80% packet loss, time 76ms > > > > rtt min/avg/max/mdev = 6848.316/6848.316/6848.316/0.000 ms, pipe 4 > > > > -- > > > > > > > > I cannot even use netperf. > > > > > > OK so that's the bug to try to find and fix I think. > > > > > > > > > > If I modify with my proposed version: > > > > + ping -c 5 10.200.0.1 > > > > PING 10.200.0.1 (10.200.0.1) 56(84) bytes of data. > > > > 64 bytes from 10.200.0.1: icmp_seq=1 ttl=64 time=7.07 ms > > > > 64 bytes from 10.200.0.1: icmp_seq=2 ttl=64 time=0.358 ms > > > > 64 bytes from 10.200.0.1: icmp_seq=3 ttl=64 time=5.35 ms > > > > 64 bytes from 10.200.0.1: icmp_seq=4 ttl=64 time=2.27 ms > > > > 64 bytes from 10.200.0.1: icmp_seq=5 ttl=64 time=0.426 ms > > > > > > Not sure which version this is. > > > > > > > [root@localhost ~]# netperf -H 10.200.0.1 -p 12865 -l 10 -t TCP_STREAM > > > > MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to > > > > 10.200.0.1 () port 0 AF_INET > > > > Recv Send Send > > > > Socket Socket Message Elapsed > > > > Size Size Size Time Throughput > > > > bytes bytes bytes secs. 10^6bits/sec > > > > > > > > 131072 16384 16384 10.01 4742.36 > > > > [root@localhost ~]# netperf -H 10.200.0.1 -p 12865 -l 10 -t UDP_STREAM > > > > MIGRATED UDP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to > > > > 10.200.0.1 () port 0 AF_INET > > > > Socket Message Elapsed Messages > > > > Size Size Time Okay Errors Throughput > > > > bytes bytes secs # # 10^6bits/sec > > > > > > > > 212992 65507 10.00 9214 0 482.83 > > > > 212992 10.00 9214 482.83 > > > > > > > > I will compare with the non-batch version for reference, but the > > > > difference between the two is noticeable. Maybe it's worth finding a > > > > good value for the if() inside fetch_buf? > > > > > > > > Thanks! > > > > > > > > > > I don't think it's performance, I think it's a bug somewhere, > > > e.g. maybe we corrupt a packet, or stall the queue, or > > > something like this. > > > > > > Let's do this, I will squash the fixups and post v8 so you can bisect > > > and then debug cleanly. > > > > Ok, so if we apply the patch proposed in v7 08/14 (Or the version 8 of the patchset sent), this is what happens: > > > > 1. Userland (virtio_test in my case) introduces just one buffer in vq, and it kicks > > 2. vhost module reaches fetch_descs, called from vhost_get_vq_desc. From there we call fetch_buf in a for loop. > > 3. The first time we call fetch_buf, it returns properly one buffer. However, the second time we call it, it returns 0 > > because vq->avail_idx == vq->last_avail_idx and vq->avail_idx == last_avail_idx code path. > > 4. fetch_descs assign ret = 0, so it returns 0. vhost_get_vq_desc will goto err, and it will signal no new buffer > > (returning vq->num). > > > > So to fix it and maintain the batching maybe we could return vq->ndescs in case ret == 0: > > > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > > index c0dfb5e3d2af..5993d4f34ca9 100644 > > --- a/drivers/vhost/vhost.c > > +++ b/drivers/vhost/vhost.c > > @@ -2315,7 +2327,8 @@ static int fetch_descs(struct vhost_virtqueue *vq) > > > > /* On success we expect some descs */ > > BUG_ON(ret > 0 && !vq->ndescs); > > - return ret; > > + return ret ?: vq->ndescs; I'd rather we used standard C. Also ret < 0 needs to be handled. Also - what if fetch of some descs fails but some succeeds? What do we want to do? Maybe: return vq->ndescs ? vq->ndescs : ret; > > } > > > > /* Reverse the effects of fetch_descs */ > > -- > > > > Another possibility could be to return different codes from fetch_buf, but I find the suggested modification easier. > > > > What do you think? > > > > Thanks! > > > > Hi! > > I can send a proposed RFC v9 in case it is more convenient for you. > > Thanks! Excellent, pls go ahead! And can you include the performance numbers? It's enough to test the final version.
diff --git a/drivers/vhost/test.c b/drivers/vhost/test.c index 0466921f4772..7d69778aaa26 100644 --- a/drivers/vhost/test.c +++ b/drivers/vhost/test.c @@ -119,7 +119,7 @@ static int vhost_test_open(struct inode *inode, struct file *f) dev = &n->dev; vqs[VHOST_TEST_VQ] = &n->vqs[VHOST_TEST_VQ]; n->vqs[VHOST_TEST_VQ].handle_kick = handle_vq_kick; - vhost_dev_init(dev, vqs, VHOST_TEST_VQ_MAX, UIO_MAXIOV, + vhost_dev_init(dev, vqs, VHOST_TEST_VQ_MAX, UIO_MAXIOV + 64, VHOST_TEST_PKT_WEIGHT, VHOST_TEST_WEIGHT, true, NULL); f->private_data = n; diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 11433d709651..28f324fd77df 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -304,6 +304,7 @@ static void vhost_vq_reset(struct vhost_dev *dev, { vq->num = 1; vq->ndescs = 0; + vq->first_desc = 0; vq->desc = NULL; vq->avail = NULL; vq->used = NULL; @@ -372,6 +373,11 @@ static int vhost_worker(void *data) return 0; } +static int vhost_vq_num_batch_descs(struct vhost_virtqueue *vq) +{ + return vq->max_descs - UIO_MAXIOV; +} + static void vhost_vq_free_iovecs(struct vhost_virtqueue *vq) { kfree(vq->descs); @@ -394,6 +400,9 @@ static long vhost_dev_alloc_iovecs(struct vhost_dev *dev) for (i = 0; i < dev->nvqs; ++i) { vq = dev->vqs[i]; vq->max_descs = dev->iov_limit; + if (vhost_vq_num_batch_descs(vq) < 0) { + return -EINVAL; + } vq->descs = kmalloc_array(vq->max_descs, sizeof(*vq->descs), GFP_KERNEL); @@ -1610,6 +1619,7 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg vq->last_avail_idx = s.num; /* Forget the cached index value. */ vq->avail_idx = vq->last_avail_idx; + vq->ndescs = vq->first_desc = 0; break; case VHOST_GET_VRING_BASE: s.index = idx; @@ -2078,253 +2088,6 @@ static unsigned next_desc(struct vhost_virtqueue *vq, struct vring_desc *desc) return next; } -static int get_indirect(struct vhost_virtqueue *vq, - struct iovec iov[], unsigned int iov_size, - unsigned int *out_num, unsigned int *in_num, - struct vhost_log *log, unsigned int *log_num, - struct vring_desc *indirect) -{ - struct vring_desc desc; - unsigned int i = 0, count, found = 0; - u32 len = vhost32_to_cpu(vq, indirect->len); - struct iov_iter from; - int ret, access; - - /* Sanity check */ - if (unlikely(len % sizeof desc)) { - vq_err(vq, "Invalid length in indirect descriptor: " - "len 0x%llx not multiple of 0x%zx\n", - (unsigned long long)len, - sizeof desc); - return -EINVAL; - } - - ret = translate_desc(vq, vhost64_to_cpu(vq, indirect->addr), len, vq->indirect, - UIO_MAXIOV, VHOST_ACCESS_RO); - if (unlikely(ret < 0)) { - if (ret != -EAGAIN) - vq_err(vq, "Translation failure %d in indirect.\n", ret); - return ret; - } - iov_iter_init(&from, READ, vq->indirect, ret, len); - - /* We will use the result as an address to read from, so most - * architectures only need a compiler barrier here. */ - read_barrier_depends(); - - count = len / sizeof desc; - /* Buffers are chained via a 16 bit next field, so - * we can have at most 2^16 of these. */ - if (unlikely(count > USHRT_MAX + 1)) { - vq_err(vq, "Indirect buffer length too big: %d\n", - indirect->len); - return -E2BIG; - } - - do { - unsigned iov_count = *in_num + *out_num; - if (unlikely(++found > count)) { - vq_err(vq, "Loop detected: last one at %u " - "indirect size %u\n", - i, count); - return -EINVAL; - } - if (unlikely(!copy_from_iter_full(&desc, sizeof(desc), &from))) { - vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n", - i, (size_t)vhost64_to_cpu(vq, indirect->addr) + i * sizeof desc); - return -EINVAL; - } - if (unlikely(desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_INDIRECT))) { - vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n", - i, (size_t)vhost64_to_cpu(vq, indirect->addr) + i * sizeof desc); - return -EINVAL; - } - - if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_WRITE)) - access = VHOST_ACCESS_WO; - else - access = VHOST_ACCESS_RO; - - ret = translate_desc(vq, vhost64_to_cpu(vq, desc.addr), - vhost32_to_cpu(vq, desc.len), iov + iov_count, - iov_size - iov_count, access); - if (unlikely(ret < 0)) { - if (ret != -EAGAIN) - vq_err(vq, "Translation failure %d indirect idx %d\n", - ret, i); - return ret; - } - /* If this is an input descriptor, increment that count. */ - if (access == VHOST_ACCESS_WO) { - *in_num += ret; - if (unlikely(log && ret)) { - log[*log_num].addr = vhost64_to_cpu(vq, desc.addr); - log[*log_num].len = vhost32_to_cpu(vq, desc.len); - ++*log_num; - } - } else { - /* If it's an output descriptor, they're all supposed - * to come before any input descriptors. */ - if (unlikely(*in_num)) { - vq_err(vq, "Indirect descriptor " - "has out after in: idx %d\n", i); - return -EINVAL; - } - *out_num += ret; - } - } while ((i = next_desc(vq, &desc)) != -1); - return 0; -} - -/* This looks in the virtqueue and for the first available buffer, and converts - * it to an iovec for convenient access. Since descriptors consist of some - * number of output then some number of input descriptors, it's actually two - * iovecs, but we pack them into one and note how many of each there were. - * - * This function returns the descriptor number found, or vq->num (which is - * never a valid descriptor number) if none was found. A negative code is - * returned on error. */ -int vhost_get_vq_desc(struct vhost_virtqueue *vq, - struct iovec iov[], unsigned int iov_size, - unsigned int *out_num, unsigned int *in_num, - struct vhost_log *log, unsigned int *log_num) -{ - struct vring_desc desc; - unsigned int i, head, found = 0; - u16 last_avail_idx; - __virtio16 avail_idx; - __virtio16 ring_head; - int ret, access; - - /* Check it isn't doing very strange things with descriptor numbers. */ - last_avail_idx = vq->last_avail_idx; - - if (vq->avail_idx == vq->last_avail_idx) { - if (unlikely(vhost_get_avail_idx(vq, &avail_idx))) { - vq_err(vq, "Failed to access avail idx at %p\n", - &vq->avail->idx); - return -EFAULT; - } - vq->avail_idx = vhost16_to_cpu(vq, avail_idx); - - if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) { - vq_err(vq, "Guest moved used index from %u to %u", - last_avail_idx, vq->avail_idx); - return -EFAULT; - } - - /* If there's nothing new since last we looked, return - * invalid. - */ - if (vq->avail_idx == last_avail_idx) - return vq->num; - - /* Only get avail ring entries after they have been - * exposed by guest. - */ - smp_rmb(); - } - - /* Grab the next descriptor number they're advertising, and increment - * the index we've seen. */ - if (unlikely(vhost_get_avail_head(vq, &ring_head, last_avail_idx))) { - vq_err(vq, "Failed to read head: idx %d address %p\n", - last_avail_idx, - &vq->avail->ring[last_avail_idx % vq->num]); - return -EFAULT; - } - - head = vhost16_to_cpu(vq, ring_head); - - /* If their number is silly, that's an error. */ - if (unlikely(head >= vq->num)) { - vq_err(vq, "Guest says index %u > %u is available", - head, vq->num); - return -EINVAL; - } - - /* When we start there are none of either input nor output. */ - *out_num = *in_num = 0; - if (unlikely(log)) - *log_num = 0; - - i = head; - do { - unsigned iov_count = *in_num + *out_num; - if (unlikely(i >= vq->num)) { - vq_err(vq, "Desc index is %u > %u, head = %u", - i, vq->num, head); - return -EINVAL; - } - if (unlikely(++found > vq->num)) { - vq_err(vq, "Loop detected: last one at %u " - "vq size %u head %u\n", - i, vq->num, head); - return -EINVAL; - } - ret = vhost_get_desc(vq, &desc, i); - if (unlikely(ret)) { - vq_err(vq, "Failed to get descriptor: idx %d addr %p\n", - i, vq->desc + i); - return -EFAULT; - } - if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_INDIRECT)) { - ret = get_indirect(vq, iov, iov_size, - out_num, in_num, - log, log_num, &desc); - if (unlikely(ret < 0)) { - if (ret != -EAGAIN) - vq_err(vq, "Failure detected " - "in indirect descriptor at idx %d\n", i); - return ret; - } - continue; - } - - if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_WRITE)) - access = VHOST_ACCESS_WO; - else - access = VHOST_ACCESS_RO; - ret = translate_desc(vq, vhost64_to_cpu(vq, desc.addr), - vhost32_to_cpu(vq, desc.len), iov + iov_count, - iov_size - iov_count, access); - if (unlikely(ret < 0)) { - if (ret != -EAGAIN) - vq_err(vq, "Translation failure %d descriptor idx %d\n", - ret, i); - return ret; - } - if (access == VHOST_ACCESS_WO) { - /* If this is an input descriptor, - * increment that count. */ - *in_num += ret; - if (unlikely(log && ret)) { - log[*log_num].addr = vhost64_to_cpu(vq, desc.addr); - log[*log_num].len = vhost32_to_cpu(vq, desc.len); - ++*log_num; - } - } else { - /* If it's an output descriptor, they're all supposed - * to come before any input descriptors. */ - if (unlikely(*in_num)) { - vq_err(vq, "Descriptor has out after in: " - "idx %d\n", i); - return -EINVAL; - } - *out_num += ret; - } - } while ((i = next_desc(vq, &desc)) != -1); - - /* On success, increment avail index. */ - vq->last_avail_idx++; - - /* Assume notifications from guest are disabled at this point, - * if they aren't we would need to update avail_event index. */ - BUG_ON(!(vq->used_flags & VRING_USED_F_NO_NOTIFY)); - return head; -} -EXPORT_SYMBOL_GPL(vhost_get_vq_desc); - static struct vhost_desc *peek_split_desc(struct vhost_virtqueue *vq) { BUG_ON(!vq->ndescs); @@ -2428,7 +2191,7 @@ static int fetch_indirect_descs(struct vhost_virtqueue *vq, /* This function returns a value > 0 if a descriptor was found, or 0 if none were found. * A negative code is returned on error. */ -static int fetch_descs(struct vhost_virtqueue *vq) +static int fetch_buf(struct vhost_virtqueue *vq) { unsigned int i, head, found = 0; struct vhost_desc *last; @@ -2441,7 +2204,11 @@ static int fetch_descs(struct vhost_virtqueue *vq) /* Check it isn't doing very strange things with descriptor numbers. */ last_avail_idx = vq->last_avail_idx; - if (vq->avail_idx == vq->last_avail_idx) { + if (unlikely(vq->avail_idx == vq->last_avail_idx)) { + /* If we already have work to do, don't bother re-checking. */ + if (likely(vq->ndescs)) + return 1; + if (unlikely(vhost_get_avail_idx(vq, &avail_idx))) { vq_err(vq, "Failed to access avail idx at %p\n", &vq->avail->idx); @@ -2532,6 +2299,41 @@ static int fetch_descs(struct vhost_virtqueue *vq) return 1; } +/* This function returns a value > 0 if a descriptor was found, or 0 if none were found. + * A negative code is returned on error. */ +static int fetch_descs(struct vhost_virtqueue *vq) +{ + int ret; + + if (unlikely(vq->first_desc >= vq->ndescs)) { + vq->first_desc = 0; + vq->ndescs = 0; + } + + if (vq->ndescs) + return 1; + + for (ret = 1; + ret > 0 && vq->ndescs <= vhost_vq_num_batch_descs(vq); + ret = fetch_buf(vq)) + ; + + /* On success we expect some descs */ + BUG_ON(ret > 0 && !vq->ndescs); + return ret; +} + +/* Reverse the effects of fetch_descs */ +static void unfetch_descs(struct vhost_virtqueue *vq) +{ + int i; + + for (i = vq->first_desc; i < vq->ndescs; ++i) + if (!(vq->descs[i].flags & VRING_DESC_F_NEXT)) + vq->last_avail_idx -= 1; + vq->ndescs = 0; +} + /* This looks in the virtqueue and for the first available buffer, and converts * it to an iovec for convenient access. Since descriptors consist of some * number of output then some number of input descriptors, it's actually two @@ -2540,7 +2342,7 @@ static int fetch_descs(struct vhost_virtqueue *vq) * This function returns the descriptor number found, or vq->num (which is * never a valid descriptor number) if none was found. A negative code is * returned on error. */ -int vhost_get_vq_desc_batch(struct vhost_virtqueue *vq, +int vhost_get_vq_desc(struct vhost_virtqueue *vq, struct iovec iov[], unsigned int iov_size, unsigned int *out_num, unsigned int *in_num, struct vhost_log *log, unsigned int *log_num) @@ -2549,7 +2351,7 @@ int vhost_get_vq_desc_batch(struct vhost_virtqueue *vq, int i; if (ret <= 0) - goto err_fetch; + goto err; /* Now convert to IOV */ /* When we start there are none of either input nor output. */ @@ -2557,7 +2359,7 @@ int vhost_get_vq_desc_batch(struct vhost_virtqueue *vq, if (unlikely(log)) *log_num = 0; - for (i = 0; i < vq->ndescs; ++i) { + for (i = vq->first_desc; i < vq->ndescs; ++i) { unsigned iov_count = *in_num + *out_num; struct vhost_desc *desc = &vq->descs[i]; int access; @@ -2603,24 +2405,26 @@ int vhost_get_vq_desc_batch(struct vhost_virtqueue *vq, } ret = desc->id; + + if (!(desc->flags & VRING_DESC_F_NEXT)) + break; } - vq->ndescs = 0; + vq->first_desc = i + 1; return ret; err: - vhost_discard_vq_desc(vq, 1); -err_fetch: - vq->ndescs = 0; + unfetch_descs(vq); return ret ? ret : vq->num; } -EXPORT_SYMBOL_GPL(vhost_get_vq_desc_batch); +EXPORT_SYMBOL_GPL(vhost_get_vq_desc); /* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */ void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n) { + unfetch_descs(vq); vq->last_avail_idx -= n; } EXPORT_SYMBOL_GPL(vhost_discard_vq_desc); diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h index 87089d51490d..fed36af5c444 100644 --- a/drivers/vhost/vhost.h +++ b/drivers/vhost/vhost.h @@ -81,6 +81,7 @@ struct vhost_virtqueue { struct vhost_desc *descs; int ndescs; + int first_desc; int max_descs; struct file *kick; @@ -189,10 +190,6 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg bool vhost_vq_access_ok(struct vhost_virtqueue *vq); bool vhost_log_access_ok(struct vhost_dev *); -int vhost_get_vq_desc_batch(struct vhost_virtqueue *, - struct iovec iov[], unsigned int iov_count, - unsigned int *out_num, unsigned int *in_num, - struct vhost_log *log, unsigned int *log_num); int vhost_get_vq_desc(struct vhost_virtqueue *, struct iovec iov[], unsigned int iov_count, unsigned int *out_num, unsigned int *in_num, @@ -261,6 +258,8 @@ static inline void vhost_vq_set_backend(struct vhost_virtqueue *vq, void *private_data) { vq->private_data = private_data; + vq->ndescs = 0; + vq->first_desc = 0; } /**