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 <wency@cn.fujitsu.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Tested-by: Li Zhijian <lizhijian@cn.fujitsu.com>
Message-id: 1427997044-392-1-git-send-email-pbonzini@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 1 insertions, 0 deletions

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;