From: Alexander Duyck <alexander.h.du...@linux.intel.com> There is already locking in place when we are stopping free page hinting but there is not similar protections in place when we start. I can only assume this was overlooked as in most cases the page hinting should not be occurring when we are starting the hinting, however there is still a chance we could be processing hints by the time we get back around to restarting the hinting so we are better off making sure to protect the state with the mutex lock rather than just updating the value with no protections.
Based on feedback from Peter Maydell this issue had also been spotted by Coverity: CID 1430269 Acked-by: David Hildenbrand <da...@redhat.com> Signed-off-by: Alexander Duyck <alexander.h.du...@linux.intel.com> --- hw/virtio/virtio-balloon.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c index ce70adcc6925..6e2d1293402f 100644 --- a/hw/virtio/virtio-balloon.c +++ b/hw/virtio/virtio-balloon.c @@ -592,6 +592,8 @@ static void virtio_balloon_free_page_start(VirtIOBalloon *s) return; } + qemu_mutex_lock(&s->free_page_lock); + if (s->free_page_report_cmd_id == UINT_MAX) { s->free_page_report_cmd_id = VIRTIO_BALLOON_FREE_PAGE_REPORT_CMD_ID_MIN; @@ -600,6 +602,8 @@ static void virtio_balloon_free_page_start(VirtIOBalloon *s) } s->free_page_report_status = FREE_PAGE_REPORT_S_REQUESTED; + qemu_mutex_unlock(&s->free_page_lock); + virtio_notify_config(vdev); }