| Message ID | 20200508213010.26071.6318.stgit@localhost.localdomain (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | virtio-balloon: add support for page poison reporting and free page reporting | expand |
On Fri, May 8, 2020 at 2:30 PM Alexander Duyck <alexander.duyck@gmail.com> wrote: > > From: Alexander Duyck <alexander.h.duyck@linux.intel.com> > > Add support for free page reporting. The idea is to function very similar > to how the balloon works in that we basically end up madvising the page as > not being used. However we don't really need to bother with any deflate > type logic since the page will be faulted back into the guest when it is > read or written to. > > This provides a new way of letting the guest proactively report free > pages to the hypervisor, so the hypervisor can reuse them. In contrast to > inflate/deflate that is triggered via the hypervisor explicitly. > > Acked-by: David Hildenbrand <david@redhat.com> > Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com> I just realized that the patch below added the code to add the reporting_vq but I never cleaned it up. I will submit a v25 in the next couple of days that contains a fix for that. > --- > hw/virtio/virtio-balloon.c | 69 ++++++++++++++++++++++++++++++++++++ > include/hw/virtio/virtio-balloon.h | 2 + > 2 files changed, 70 insertions(+), 1 deletion(-) > > diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c > index 1666132a24c1..53abba290274 100644 > --- a/hw/virtio/virtio-balloon.c > +++ b/hw/virtio/virtio-balloon.c > @@ -321,6 +321,67 @@ static void balloon_stats_set_poll_interval(Object *obj, Visitor *v, > balloon_stats_change_timer(s, 0); > } > > +static void virtio_balloon_handle_report(VirtIODevice *vdev, VirtQueue *vq) > +{ > + VirtIOBalloon *dev = VIRTIO_BALLOON(vdev); > + VirtQueueElement *elem; > + > + while ((elem = virtqueue_pop(vq, sizeof(VirtQueueElement)))) { > + unsigned int i; > + > + /* > + * When we discard the page it has the effect of removing the page > + * from the hypervisor itself and causing it to be zeroed when it > + * is returned to us. So we must not discard the page if it is > + * accessible by another device or process, or if the guest is > + * expecting it to retain a non-zero value. > + */ > + if (qemu_balloon_is_inhibited() || dev->poison_val) { > + goto skip_element; > + } > + > + for (i = 0; i < elem->in_num; i++) { > + void *addr = elem->in_sg[i].iov_base; > + size_t size = elem->in_sg[i].iov_len; > + ram_addr_t ram_offset; > + RAMBlock *rb; > + > + /* > + * There is no need to check the memory section to see if > + * it is ram/readonly/romd like there is for handle_output > + * below. If the region is not meant to be written to then > + * address_space_map will have allocated a bounce buffer > + * and it will be freed in address_space_unmap and trigger > + * and unassigned_mem_write before failing to copy over the > + * buffer. If more than one bad descriptor is provided it > + * will return NULL after the first bounce buffer and fail > + * to map any resources. > + */ > + rb = qemu_ram_block_from_host(addr, false, &ram_offset); > + if (!rb) { > + trace_virtio_balloon_bad_addr(elem->in_addr[i]); > + continue; > + } > + > + /* > + * For now we will simply ignore unaligned memory regions, or > + * regions that overrun the end of the RAMBlock. > + */ > + if (!QEMU_IS_ALIGNED(ram_offset | size, qemu_ram_pagesize(rb)) || > + (ram_offset + size) > qemu_ram_get_used_length(rb)) { > + continue; > + } > + > + ram_block_discard_range(rb, ram_offset, size); > + } > + > +skip_element: > + virtqueue_push(vq, elem, 0); > + virtio_notify(vdev, vq); > + g_free(elem); > + } > +} > + > static void virtio_balloon_handle_output(VirtIODevice *vdev, VirtQueue *vq) > { > VirtIOBalloon *s = VIRTIO_BALLOON(vdev); > @@ -841,6 +902,12 @@ static void virtio_balloon_device_realize(DeviceState *dev, Error **errp) > virtio_error(vdev, "iothread is missing"); > } > } > + > + if (virtio_has_feature(s->host_features, VIRTIO_BALLOON_F_REPORTING)) { > + s->reporting_vq = virtio_add_queue(vdev, 32, > + virtio_balloon_handle_report); > + } > + > reset_stats(s); > } > > @@ -945,6 +1012,8 @@ static Property virtio_balloon_properties[] = { > VIRTIO_BALLOON_F_FREE_PAGE_HINT, false), > DEFINE_PROP_BIT("page-poison", VirtIOBalloon, host_features, > VIRTIO_BALLOON_F_PAGE_POISON, true), > + DEFINE_PROP_BIT("free-page-reporting", VirtIOBalloon, host_features, > + VIRTIO_BALLOON_F_REPORTING, false), > /* QEMU 4.0 accidentally changed the config size even when free-page-hint > * is disabled, resulting in QEMU 3.1 migration incompatibility. This > * property retains this quirk for QEMU 4.1 machine types. > diff --git a/include/hw/virtio/virtio-balloon.h b/include/hw/virtio/virtio-balloon.h > index 3ca2a78e1aca..28fd2b396087 100644 > --- a/include/hw/virtio/virtio-balloon.h > +++ b/include/hw/virtio/virtio-balloon.h > @@ -42,7 +42,7 @@ enum virtio_balloon_free_page_hint_status { > > typedef struct VirtIOBalloon { > VirtIODevice parent_obj; > - VirtQueue *ivq, *dvq, *svq, *free_page_vq; > + VirtQueue *ivq, *dvq, *svq, *free_page_vq, *reporting_vq; > uint32_t free_page_hint_status; > uint32_t num_pages; > uint32_t actual; >
diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c index 1666132a24c1..53abba290274 100644 --- a/hw/virtio/virtio-balloon.c +++ b/hw/virtio/virtio-balloon.c @@ -321,6 +321,67 @@ static void balloon_stats_set_poll_interval(Object *obj, Visitor *v, balloon_stats_change_timer(s, 0); } +static void virtio_balloon_handle_report(VirtIODevice *vdev, VirtQueue *vq) +{ + VirtIOBalloon *dev = VIRTIO_BALLOON(vdev); + VirtQueueElement *elem; + + while ((elem = virtqueue_pop(vq, sizeof(VirtQueueElement)))) { + unsigned int i; + + /* + * When we discard the page it has the effect of removing the page + * from the hypervisor itself and causing it to be zeroed when it + * is returned to us. So we must not discard the page if it is + * accessible by another device or process, or if the guest is + * expecting it to retain a non-zero value. + */ + if (qemu_balloon_is_inhibited() || dev->poison_val) { + goto skip_element; + } + + for (i = 0; i < elem->in_num; i++) { + void *addr = elem->in_sg[i].iov_base; + size_t size = elem->in_sg[i].iov_len; + ram_addr_t ram_offset; + RAMBlock *rb; + + /* + * There is no need to check the memory section to see if + * it is ram/readonly/romd like there is for handle_output + * below. If the region is not meant to be written to then + * address_space_map will have allocated a bounce buffer + * and it will be freed in address_space_unmap and trigger + * and unassigned_mem_write before failing to copy over the + * buffer. If more than one bad descriptor is provided it + * will return NULL after the first bounce buffer and fail + * to map any resources. + */ + rb = qemu_ram_block_from_host(addr, false, &ram_offset); + if (!rb) { + trace_virtio_balloon_bad_addr(elem->in_addr[i]); + continue; + } + + /* + * For now we will simply ignore unaligned memory regions, or + * regions that overrun the end of the RAMBlock. + */ + if (!QEMU_IS_ALIGNED(ram_offset | size, qemu_ram_pagesize(rb)) || + (ram_offset + size) > qemu_ram_get_used_length(rb)) { + continue; + } + + ram_block_discard_range(rb, ram_offset, size); + } + +skip_element: + virtqueue_push(vq, elem, 0); + virtio_notify(vdev, vq); + g_free(elem); + } +} + static void virtio_balloon_handle_output(VirtIODevice *vdev, VirtQueue *vq) { VirtIOBalloon *s = VIRTIO_BALLOON(vdev); @@ -841,6 +902,12 @@ static void virtio_balloon_device_realize(DeviceState *dev, Error **errp) virtio_error(vdev, "iothread is missing"); } } + + if (virtio_has_feature(s->host_features, VIRTIO_BALLOON_F_REPORTING)) { + s->reporting_vq = virtio_add_queue(vdev, 32, + virtio_balloon_handle_report); + } + reset_stats(s); } @@ -945,6 +1012,8 @@ static Property virtio_balloon_properties[] = { VIRTIO_BALLOON_F_FREE_PAGE_HINT, false), DEFINE_PROP_BIT("page-poison", VirtIOBalloon, host_features, VIRTIO_BALLOON_F_PAGE_POISON, true), + DEFINE_PROP_BIT("free-page-reporting", VirtIOBalloon, host_features, + VIRTIO_BALLOON_F_REPORTING, false), /* QEMU 4.0 accidentally changed the config size even when free-page-hint * is disabled, resulting in QEMU 3.1 migration incompatibility. This * property retains this quirk for QEMU 4.1 machine types. diff --git a/include/hw/virtio/virtio-balloon.h b/include/hw/virtio/virtio-balloon.h index 3ca2a78e1aca..28fd2b396087 100644 --- a/include/hw/virtio/virtio-balloon.h +++ b/include/hw/virtio/virtio-balloon.h @@ -42,7 +42,7 @@ enum virtio_balloon_free_page_hint_status { typedef struct VirtIOBalloon { VirtIODevice parent_obj; - VirtQueue *ivq, *dvq, *svq, *free_page_vq; + VirtQueue *ivq, *dvq, *svq, *free_page_vq, *reporting_vq; uint32_t free_page_hint_status; uint32_t num_pages; uint32_t actual;