| Message ID | 20210219101919.91069-1-akihiko.odaki@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | virtio-blk: Respect discard granularity | expand |
On Fri, Feb 19, 2021 at 07:19:19PM +0900, Akihiko Odaki wrote: > Signed-off-by: Akihiko Odaki <akihiko.odaki@gmail.com> > --- > hw/block/virtio-blk.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c > index bac2d6fa2b2..692fd17b0e0 100644 > --- a/hw/block/virtio-blk.c > +++ b/hw/block/virtio-blk.c > @@ -965,7 +965,7 @@ static void virtio_blk_update_config(VirtIODevice *vdev, uint8_t *config) > virtio_stl_p(vdev, &blkcfg.max_discard_sectors, > s->conf.max_discard_sectors); > virtio_stl_p(vdev, &blkcfg.discard_sector_alignment, > - blk_size >> BDRV_SECTOR_BITS); > + conf->discard_granularity >> BDRV_SECTOR_BITS); Please handle the -1 default value like this: uint32_t discard_granularity = conf->discard_granularity; if (conf->discard_granularity == -1) { discard_granularity = BDRV_SECTOR_SIZE; } I noticed this when comparing the blk_size and discard_granularity values when I run QEMU: $ qemu-system-x86_64 -M accel=kvm -m 1G -cpu host -drive if=virtio,file=test.img,format=raw blk_size 512 discard_granularity 4294967295 Also, please add a compat prop in hw/core/machine.c to ensure that existing machine types are unaffected by this change. This can be done by adding DEFINE_PROP_BOOL("report-discard-granularity", ...) in hw/block/virtio-blk.c and then setting it to false for existing machine types in hw/core/machine.c. Then new machine types benefit from the new feature but existing machine types will be unchanged (eliminating the risk of live migration/snapshot incompatibilities when the device unexpectedly changes behavior while the guest is running). Stefan
diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c index bac2d6fa2b2..692fd17b0e0 100644 --- a/hw/block/virtio-blk.c +++ b/hw/block/virtio-blk.c @@ -965,7 +965,7 @@ static void virtio_blk_update_config(VirtIODevice *vdev, uint8_t *config) virtio_stl_p(vdev, &blkcfg.max_discard_sectors, s->conf.max_discard_sectors); virtio_stl_p(vdev, &blkcfg.discard_sector_alignment, - blk_size >> BDRV_SECTOR_BITS); + conf->discard_granularity >> BDRV_SECTOR_BITS); /* * We support only one segment per request since multiple segments * are not widely used and there are no userspace APIs that allow
Signed-off-by: Akihiko Odaki <akihiko.odaki@gmail.com> --- hw/block/virtio-blk.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)