By the virtio spec [*] the vring is aligned, so the 'idx' and 'flag' fields are also 16-bit aligned. Therefore we can use the load/store *aligned* API to set the value.
[*] https://docs.oasis-open.org/virtio/virtio/v1.1/csprd01/virtio-v1.1-csprd01.html#x1-430008 Reported-by: Bibo Mao <maob...@loongson.cn> Inspired-by: Stefan Hajnoczi <stefa...@redhat.com> Signed-off-by: Philippe Mathieu-Daudé <phi...@redhat.com> --- hw/virtio/virtio.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index e02544b2df7..ebee9c4e643 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -296,7 +296,7 @@ static inline uint16_t vring_avail_flags(VirtQueue *vq) return 0; } - return virtio_lduw_phys_cached(vq->vdev, &caches->avail, pa); + return virtio_lduw_phys_cached_aligned(vq->vdev, &caches->avail, pa); } /* Called within rcu_read_lock(). */ @@ -309,7 +309,8 @@ static inline uint16_t vring_avail_idx(VirtQueue *vq) return 0; } - vq->shadow_avail_idx = virtio_lduw_phys_cached(vq->vdev, &caches->avail, pa); + vq->shadow_avail_idx = virtio_lduw_phys_cached_aligned(vq->vdev, + &caches->avail, pa); return vq->shadow_avail_idx; } @@ -359,7 +360,7 @@ static uint16_t vring_used_idx(VirtQueue *vq) return 0; } - return virtio_lduw_phys_cached(vq->vdev, &caches->used, pa); + return virtio_lduw_phys_cached_aligned(vq->vdev, &caches->used, pa); } /* Called within rcu_read_lock(). */ @@ -369,7 +370,7 @@ static inline void vring_used_idx_set(VirtQueue *vq, uint16_t val) hwaddr pa = offsetof(VRingUsed, idx); if (caches) { - virtio_stw_phys_cached(vq->vdev, &caches->used, pa, val); + virtio_stw_phys_cached_aligned(vq->vdev, &caches->used, pa, val); address_space_cache_invalidate(&caches->used, pa, sizeof(val)); } @@ -388,8 +389,8 @@ static inline void vring_used_flags_set_bit(VirtQueue *vq, int mask) return; } - flags = virtio_lduw_phys_cached(vq->vdev, &caches->used, pa); - virtio_stw_phys_cached(vdev, &caches->used, pa, flags | mask); + flags = virtio_lduw_phys_cached_aligned(vq->vdev, &caches->used, pa); + virtio_stw_phys_cached_aligned(vdev, &caches->used, pa, flags | mask); address_space_cache_invalidate(&caches->used, pa, sizeof(flags)); } -- 2.26.3
