Add missing memory barriers in virtio:
- before checking interrupt enabled bit, make sure
data has been written to memory
- make sure ring index has been read before reading ring data
Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
---
hw/virtio.c | 8 +++++++-
1 files changed, 7 insertions(+), 1 deletions(-)
diff --git a/hw/virtio.c b/hw/virtio.c
index 9f020cf..bbd7b51 100644
--- a/hw/virtio.c
+++ b/hw/virtio.c
@@ -119,8 +119,12 @@ static inline uint16_t vring_avail_flags(VirtQueue *vq)
static inline uint16_t vring_avail_idx(VirtQueue *vq)
{
target_phys_addr_t pa;
+ uint16_t idx;
pa = vq->vring.avail + offsetof(VRingAvail, idx);
- return lduw_phys(pa);
+ idx = lduw_phys(pa);
+ /* Make sure data read happens after index read */
+ rmb();
+ return idx;
}
static inline uint16_t vring_avail_ring(VirtQueue *vq, int i)
@@ -588,6 +592,8 @@ VirtQueue *virtio_add_queue(VirtIODevice *vdev, int
queue_size,
void virtio_notify(VirtIODevice *vdev, VirtQueue *vq)
{
+ /* Make sure used ring is updated before we check NO_INTERRUPT. */
+ mb();
/* Always notify when queue is empty (when feature acknowledge) */
if ((vring_avail_flags(vq) & VRING_AVAIL_F_NO_INTERRUPT) &&
(!(vdev->features & (1 << VIRTIO_F_NOTIFY_ON_EMPTY)) ||
--
1.6.5.2.143.g8cc62
