| Message ID | 20210128144127.113245-3-sgarzare@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | vdpa: add vdpa simulator for block device | expand |
On 2021/1/28 下午10:41, Stefano Garzarella wrote: > Usually iotlb accesses are synchronized with a spinlock. > Let's request it as a new parameter in vringh_set_iotlb() and > hold it when we navigate the iotlb in iotlb_translate() to avoid > race conditions with any new additions/deletions of ranges from > the ioltb. Patch looks fine but I wonder if this is the best approach comparing to do locking by the caller. Thanks > > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> > --- > include/linux/vringh.h | 6 +++++- > drivers/vdpa/vdpa_sim/vdpa_sim.c | 3 ++- > drivers/vhost/vringh.c | 9 ++++++++- > 3 files changed, 15 insertions(+), 3 deletions(-) > > diff --git a/include/linux/vringh.h b/include/linux/vringh.h > index 59bd50f99291..9c077863c8f6 100644 > --- a/include/linux/vringh.h > +++ b/include/linux/vringh.h > @@ -46,6 +46,9 @@ struct vringh { > /* IOTLB for this vring */ > struct vhost_iotlb *iotlb; > > + /* spinlock to synchronize IOTLB accesses */ > + spinlock_t *iotlb_lock; > + > /* The function to call to notify the guest about added buffers */ > void (*notify)(struct vringh *); > }; > @@ -258,7 +261,8 @@ static inline __virtio64 cpu_to_vringh64(const struct vringh *vrh, u64 val) > > #if IS_REACHABLE(CONFIG_VHOST_IOTLB) > > -void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb); > +void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb, > + spinlock_t *iotlb_lock); > > int vringh_init_iotlb(struct vringh *vrh, u64 features, > unsigned int num, bool weak_barriers, > diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c > index 2183a833fcf4..53238989713d 100644 > --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c > +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c > @@ -284,7 +284,8 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr) > goto err_iommu; > > for (i = 0; i < dev_attr->nvqs; i++) > - vringh_set_iotlb(&vdpasim->vqs[i].vring, vdpasim->iommu); > + vringh_set_iotlb(&vdpasim->vqs[i].vring, vdpasim->iommu, > + &vdpasim->iommu_lock); > > ret = iova_cache_get(); > if (ret) > diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c > index 85d85faba058..f68122705719 100644 > --- a/drivers/vhost/vringh.c > +++ b/drivers/vhost/vringh.c > @@ -1074,6 +1074,8 @@ static int iotlb_translate(const struct vringh *vrh, > int ret = 0; > u64 s = 0; > > + spin_lock(vrh->iotlb_lock); > + > while (len > s) { > u64 size, pa, pfn; > > @@ -1103,6 +1105,8 @@ static int iotlb_translate(const struct vringh *vrh, > ++ret; > } > > + spin_unlock(vrh->iotlb_lock); > + > return ret; > } > > @@ -1262,10 +1266,13 @@ EXPORT_SYMBOL(vringh_init_iotlb); > * vringh_set_iotlb - initialize a vringh for a ring with IOTLB. > * @vrh: the vring > * @iotlb: iotlb associated with this vring > + * @iotlb_lock: spinlock to synchronize the iotlb accesses > */ > -void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb) > +void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb, > + spinlock_t *iotlb_lock) > { > vrh->iotlb = iotlb; > + vrh->iotlb_lock = iotlb_lock; > } > EXPORT_SYMBOL(vringh_set_iotlb); >
On 2021/1/29 下午5:18, Stefano Garzarella wrote: > On Fri, Jan 29, 2021 at 03:43:40PM +0800, Jason Wang wrote: >> >> On 2021/1/28 下午10:41, Stefano Garzarella wrote: >>> Usually iotlb accesses are synchronized with a spinlock. >>> Let's request it as a new parameter in vringh_set_iotlb() and >>> hold it when we navigate the iotlb in iotlb_translate() to avoid >>> race conditions with any new additions/deletions of ranges from >>> the ioltb. >> >> >> Patch looks fine but I wonder if this is the best approach comparing >> to do locking by the caller. > > Initially I tried to hold the lock in the vdpasim_blk_work(), but since > we have a lot of different functions for vringh, I opted to take the > lock at the beginning and release it at the end. > Also because several times I went to see if that call used > iotlb_translate or not. > > This could be a problem for example if we have multiple workers to > handle multiple queues. > > Also, some functions are quite long (e.g. vringh_getdesc_iotlb) and > holding the lock for that long could reduce parallelism. > > For these reasons I thought it was better to hide everything from the > caller who doesn't have to worry about which function calls > iotlb_translate() and thus hold the lock. Fine with me. Acked-by: Jason Wang <jasowang@redhat.com> Thanks > > Thanks, > Stefano > >> >> Thanks >> >> >>> >>> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> >>> --- >>> include/linux/vringh.h | 6 +++++- >>> drivers/vdpa/vdpa_sim/vdpa_sim.c | 3 ++- >>> drivers/vhost/vringh.c | 9 ++++++++- >>> 3 files changed, 15 insertions(+), 3 deletions(-) >>> >>> diff --git a/include/linux/vringh.h b/include/linux/vringh.h >>> index 59bd50f99291..9c077863c8f6 100644 >>> --- a/include/linux/vringh.h >>> +++ b/include/linux/vringh.h >>> @@ -46,6 +46,9 @@ struct vringh { >>> /* IOTLB for this vring */ >>> struct vhost_iotlb *iotlb; >>> + /* spinlock to synchronize IOTLB accesses */ >>> + spinlock_t *iotlb_lock; >>> + >>> /* The function to call to notify the guest about added buffers */ >>> void (*notify)(struct vringh *); >>> }; >>> @@ -258,7 +261,8 @@ static inline __virtio64 cpu_to_vringh64(const >>> struct vringh *vrh, u64 val) >>> #if IS_REACHABLE(CONFIG_VHOST_IOTLB) >>> -void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb); >>> +void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb, >>> + spinlock_t *iotlb_lock); >>> int vringh_init_iotlb(struct vringh *vrh, u64 features, >>> unsigned int num, bool weak_barriers, >>> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c >>> b/drivers/vdpa/vdpa_sim/vdpa_sim.c >>> index 2183a833fcf4..53238989713d 100644 >>> --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c >>> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c >>> @@ -284,7 +284,8 @@ struct vdpasim *vdpasim_create(struct >>> vdpasim_dev_attr *dev_attr) >>> goto err_iommu; >>> for (i = 0; i < dev_attr->nvqs; i++) >>> - vringh_set_iotlb(&vdpasim->vqs[i].vring, vdpasim->iommu); >>> + vringh_set_iotlb(&vdpasim->vqs[i].vring, vdpasim->iommu, >>> + &vdpasim->iommu_lock); >>> ret = iova_cache_get(); >>> if (ret) >>> diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c >>> index 85d85faba058..f68122705719 100644 >>> --- a/drivers/vhost/vringh.c >>> +++ b/drivers/vhost/vringh.c >>> @@ -1074,6 +1074,8 @@ static int iotlb_translate(const struct vringh >>> *vrh, >>> int ret = 0; >>> u64 s = 0; >>> + spin_lock(vrh->iotlb_lock); >>> + >>> while (len > s) { >>> u64 size, pa, pfn; >>> @@ -1103,6 +1105,8 @@ static int iotlb_translate(const struct vringh >>> *vrh, >>> ++ret; >>> } >>> + spin_unlock(vrh->iotlb_lock); >>> + >>> return ret; >>> } >>> @@ -1262,10 +1266,13 @@ EXPORT_SYMBOL(vringh_init_iotlb); >>> * vringh_set_iotlb - initialize a vringh for a ring with IOTLB. >>> * @vrh: the vring >>> * @iotlb: iotlb associated with this vring >>> + * @iotlb_lock: spinlock to synchronize the iotlb accesses >>> */ >>> -void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb) >>> +void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb, >>> + spinlock_t *iotlb_lock) >>> { >>> vrh->iotlb = iotlb; >>> + vrh->iotlb_lock = iotlb_lock; >>> } >>> EXPORT_SYMBOL(vringh_set_iotlb); >> >
diff --git a/include/linux/vringh.h b/include/linux/vringh.h index 59bd50f99291..9c077863c8f6 100644 --- a/include/linux/vringh.h +++ b/include/linux/vringh.h @@ -46,6 +46,9 @@ struct vringh { /* IOTLB for this vring */ struct vhost_iotlb *iotlb; + /* spinlock to synchronize IOTLB accesses */ + spinlock_t *iotlb_lock; + /* The function to call to notify the guest about added buffers */ void (*notify)(struct vringh *); }; @@ -258,7 +261,8 @@ static inline __virtio64 cpu_to_vringh64(const struct vringh *vrh, u64 val) #if IS_REACHABLE(CONFIG_VHOST_IOTLB) -void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb); +void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb, + spinlock_t *iotlb_lock); int vringh_init_iotlb(struct vringh *vrh, u64 features, unsigned int num, bool weak_barriers, diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c index 2183a833fcf4..53238989713d 100644 --- a/drivers/vdpa/vdpa_sim/vdpa_sim.c +++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c @@ -284,7 +284,8 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr) goto err_iommu; for (i = 0; i < dev_attr->nvqs; i++) - vringh_set_iotlb(&vdpasim->vqs[i].vring, vdpasim->iommu); + vringh_set_iotlb(&vdpasim->vqs[i].vring, vdpasim->iommu, + &vdpasim->iommu_lock); ret = iova_cache_get(); if (ret) diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c index 85d85faba058..f68122705719 100644 --- a/drivers/vhost/vringh.c +++ b/drivers/vhost/vringh.c @@ -1074,6 +1074,8 @@ static int iotlb_translate(const struct vringh *vrh, int ret = 0; u64 s = 0; + spin_lock(vrh->iotlb_lock); + while (len > s) { u64 size, pa, pfn; @@ -1103,6 +1105,8 @@ static int iotlb_translate(const struct vringh *vrh, ++ret; } + spin_unlock(vrh->iotlb_lock); + return ret; } @@ -1262,10 +1266,13 @@ EXPORT_SYMBOL(vringh_init_iotlb); * vringh_set_iotlb - initialize a vringh for a ring with IOTLB. * @vrh: the vring * @iotlb: iotlb associated with this vring + * @iotlb_lock: spinlock to synchronize the iotlb accesses */ -void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb) +void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb, + spinlock_t *iotlb_lock) { vrh->iotlb = iotlb; + vrh->iotlb_lock = iotlb_lock; } EXPORT_SYMBOL(vringh_set_iotlb);
Usually iotlb accesses are synchronized with a spinlock. Let's request it as a new parameter in vringh_set_iotlb() and hold it when we navigate the iotlb in iotlb_translate() to avoid race conditions with any new additions/deletions of ranges from the ioltb. Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> --- include/linux/vringh.h | 6 +++++- drivers/vdpa/vdpa_sim/vdpa_sim.c | 3 ++- drivers/vhost/vringh.c | 9 ++++++++- 3 files changed, 15 insertions(+), 3 deletions(-)