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authorPaolo Bonzini <pbonzini@redhat.com>2015-04-02 19:50:44 +0200
committerStefan Hajnoczi <stefanha@redhat.com>2015-04-08 10:39:18 +0100
commit2a6cdd6d35158bc7a6aacd92b5b0302f28ec480e (patch)
tree51b158464e2013fd972bc2401d74ca13d4281743
parente4603fe139e2161464d7e75faa3a650e31f057fc (diff)
downloadqemu-arm-2a6cdd6d35158bc7a6aacd92b5b0302f28ec480e.tar.gz
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>
-rw-r--r--hw/block/dataplane/virtio-blk.c3
-rw-r--r--hw/block/virtio-blk.c13
-rw-r--r--include/hw/virtio/virtio-blk.h1
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;