From 2a6cdd6d35158bc7a6aacd92b5b0302f28ec480e Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Thu, 2 Apr 2015 19:50:44 +0200 Subject: virtio-blk: correctly dirty guest memory After qemu_iovec_destroy, the QEMUIOVector's size is zeroed and the zero size ultimately is used to compute virtqueue_push's len argument. Therefore, reads from virtio-blk devices did not migrate their results correctly. (Writes were okay). Save the size in virtio_blk_handle_request, and use it when the request is completed. Based on a patch by Wen Congyang. Signed-off-by: Wen Congyang Signed-off-by: Paolo Bonzini Reviewed-by: Stefan Hajnoczi Tested-by: Li Zhijian Message-id: 1427997044-392-1-git-send-email-pbonzini@redhat.com Signed-off-by: Stefan Hajnoczi --- hw/block/dataplane/virtio-blk.c | 3 +-- hw/block/virtio-blk.c | 13 ++++++++++++- include/hw/virtio/virtio-blk.h | 1 + 3 files changed, 14 insertions(+), 3 deletions(-) diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c index cd41478b08..3db139b8a4 100644 --- a/hw/block/dataplane/virtio-blk.c +++ b/hw/block/dataplane/virtio-blk.c @@ -77,8 +77,7 @@ static void complete_request_vring(VirtIOBlockReq *req, unsigned char status) VirtIOBlockDataPlane *s = req->dev->dataplane; stb_p(&req->in->status, status); - vring_push(s->vdev, &req->dev->dataplane->vring, &req->elem, - req->qiov.size + sizeof(*req->in)); + vring_push(s->vdev, &req->dev->dataplane->vring, &req->elem, req->in_len); /* Suppress notification to guest by BH and its scheduled * flag because requests are completed as a batch after io diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c index 000c38d2a1..9546fd2919 100644 --- a/hw/block/virtio-blk.c +++ b/hw/block/virtio-blk.c @@ -33,6 +33,7 @@ VirtIOBlockReq *virtio_blk_alloc_request(VirtIOBlock *s) VirtIOBlockReq *req = g_slice_new(VirtIOBlockReq); req->dev = s; req->qiov.size = 0; + req->in_len = 0; req->next = NULL; req->mr_next = NULL; return req; @@ -54,7 +55,7 @@ static void virtio_blk_complete_request(VirtIOBlockReq *req, trace_virtio_blk_req_complete(req, status); stb_p(&req->in->status, status); - virtqueue_push(s->vq, &req->elem, req->qiov.size + sizeof(*req->in)); + virtqueue_push(s->vq, &req->elem, req->in_len); virtio_notify(vdev, s->vq); } @@ -102,6 +103,14 @@ static void virtio_blk_rw_complete(void *opaque, int ret) if (ret) { int p = virtio_ldl_p(VIRTIO_DEVICE(req->dev), &req->out.type); bool is_read = !(p & VIRTIO_BLK_T_OUT); + /* Note that memory may be dirtied on read failure. If the + * virtio request is not completed here, as is the case for + * BLOCK_ERROR_ACTION_STOP, the memory may not be copied + * correctly during live migration. While this is ugly, + * it is acceptable because the device is free to write to + * the memory until the request is completed (which will + * happen on the other side of the migration). + */ if (virtio_blk_handle_rw_error(req, -ret, is_read)) { continue; } @@ -496,6 +505,8 @@ void virtio_blk_handle_request(VirtIOBlockReq *req, MultiReqBuffer *mrb) exit(1); } + /* We always touch the last byte, so just see how big in_iov is. */ + req->in_len = iov_size(in_iov, in_num); req->in = (void *)in_iov[in_num - 1].iov_base + in_iov[in_num - 1].iov_len - sizeof(struct virtio_blk_inhdr); diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h index b3ffcd96b8..6bf5905c52 100644 --- a/include/hw/virtio/virtio-blk.h +++ b/include/hw/virtio/virtio-blk.h @@ -67,6 +67,7 @@ typedef struct VirtIOBlockReq { struct virtio_blk_inhdr *in; struct virtio_blk_outhdr out; QEMUIOVector qiov; + size_t in_len; struct VirtIOBlockReq *next; struct VirtIOBlockReq *mr_next; BlockAcctCookie acct; -- cgit v1.2.3