On Tue, Feb 12, 2019 at 02:01:44PM +0800, Changpeng Liu wrote: > Commit caa1ee43 "vhost-user-blk: add discard/write zeroes features support" > introduced extra fields to existing struct virtio_blk_config, when > migration was executed from older QEMU version to current head, it > will break the migration. While here, set the correct config size > when initializing the host driver, for now, discard/write zeroes > are not supported by virtio-blk host driver, so set the config > size as before, users can change config size when adding the new > feature bits support. > > Signed-off-by: Changpeng Liu <changpeng....@intel.com>
Pls rewrite commit log as suggested in this thread and repost. > --- > hw/block/virtio-blk.c | 10 ++++++---- > 1 file changed, 6 insertions(+), 4 deletions(-) > > diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c > index 9a87b3b..846b7b9 100644 > --- a/hw/block/virtio-blk.c > +++ b/hw/block/virtio-blk.c > @@ -28,6 +28,9 @@ > #include "hw/virtio/virtio-bus.h" > #include "hw/virtio/virtio-access.h" > > +#define VIRTIO_BLK_CFG_SIZE (offsetof(struct virtio_blk_config, num_queues) > + \ > + sizeof_field(struct virtio_blk_config, > num_queues)) > + I would just do offsetof(max_discard_sectors) with a comment "we don't support discard yet, hide associated config fields". > static void virtio_blk_init_request(VirtIOBlock *s, VirtQueue *vq, > VirtIOBlockReq *req) > { > @@ -761,7 +764,7 @@ static void virtio_blk_update_config(VirtIODevice *vdev, > uint8_t *config) > blkcfg.alignment_offset = 0; > blkcfg.wce = blk_enable_write_cache(s->blk); > virtio_stw_p(vdev, &blkcfg.num_queues, s->conf.num_queues); > - memcpy(config, &blkcfg, sizeof(struct virtio_blk_config)); > + memcpy(config, &blkcfg, VIRTIO_BLK_CFG_SIZE); Let's add QEMU_BUILD_BUG_ON(VIRTIO_BLK_CFG_SIZE <= sizeof(struct virtio_blk_config)) just for documentation purposes. > } > > static void virtio_blk_set_config(VirtIODevice *vdev, const uint8_t *config) > @@ -769,7 +772,7 @@ static void virtio_blk_set_config(VirtIODevice *vdev, > const uint8_t *config) > VirtIOBlock *s = VIRTIO_BLK(vdev); > struct virtio_blk_config blkcfg; > > - memcpy(&blkcfg, config, sizeof(blkcfg)); > + memcpy(&blkcfg, config, VIRTIO_BLK_CFG_SIZE); Here too, QEMU_BUILD_BUG_ON(VIRTIO_BLK_CFG_SIZE <= sizeof(blkcfg)) > > aio_context_acquire(blk_get_aio_context(s->blk)); > blk_set_enable_write_cache(s->blk, blkcfg.wce != 0); > @@ -952,8 +955,7 @@ static void virtio_blk_device_realize(DeviceState *dev, > Error **errp) > return; > } > > - virtio_init(vdev, "virtio-blk", VIRTIO_ID_BLOCK, > - sizeof(struct virtio_blk_config)); > + virtio_init(vdev, "virtio-blk", VIRTIO_ID_BLOCK, VIRTIO_BLK_CFG_SIZE); > > s->blk = conf->conf.blk; > s->rq = NULL; > -- > 1.9.3