On Fri, 11/13 14:17, Paolo Bonzini wrote: > > > On 13/11/2015 10:32, Fam Zheng wrote: > > When a request R is absorbed by request M, it is appended to the > > "mr_next" queue led by M, and is completed together with the completion > > of M, in virtio_blk_rw_complete. > > > > With error policy equals stop, if M has an I/O error, now R also gets > > prepended to the per device DMA restart queue, which will be retried > > when VM resumes. It leads to a double completion (in symptoms of memory > > corruption or use after free). > > > > Adding R to the queue is superfluous, only M needs to be in the queue. > > > > Fix this by marking request R as "merged" and skipping it in > > virtio_blk_handle_rw_error. > > > > Cc: qemu-sta...@nongnu.org > > Signed-off-by: Fam Zheng <f...@redhat.com> > > --- > > hw/block/virtio-blk.c | 9 +++++++-- > > include/hw/virtio/virtio-blk.h | 1 + > > 2 files changed, 8 insertions(+), 2 deletions(-) > > > > diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c > > index e70fccf..4871f2a 100644 > > --- a/hw/block/virtio-blk.c > > +++ b/hw/block/virtio-blk.c > > @@ -36,6 +36,7 @@ VirtIOBlockReq *virtio_blk_alloc_request(VirtIOBlock *s) > > req->in_len = 0; > > req->next = NULL; > > req->mr_next = NULL; > > + req->merged = false; > > return req; > > } > > > > @@ -72,8 +73,11 @@ static int virtio_blk_handle_rw_error(VirtIOBlockReq > > *req, int error, > > VirtIOBlock *s = req->dev; > > > > if (action == BLOCK_ERROR_ACTION_STOP) { > > - req->next = s->rq; > > - s->rq = req; > > + /* Merged requests don't need to be restarted. */ > > + if (!req->merged) { > > + req->next = s->rq; > > + s->rq = req; > > + } > > I think it still needs to be queued, so that the request is migrated > correctly. Should req->merged be checked in virtio_blk_dma_restart_bh > instead?
Yes you're right. Thanks, Fam