From f463e761a41ee71e59892121e1c74d9c25c985d2 Mon Sep 17 00:00:00 2001 From: Jason Wang Date: Thu, 11 Nov 2021 14:38:53 +0800 Subject: [PATCH] virtio: use virtio accessor to access packed descriptor flags MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit We used to access packed descriptor flags via address_space_{write|read}_cached(). When we hit the cache, memcpy() is used which is not an atomic operation which may lead a wrong value is read or wrote. So this patch switches to use virito_{stw|lduw}_phys_cached() to make sure the aceess is atomic. Fixes: 86044b24e865f ("virtio: basic packed virtqueue support") Cc: qemu-stable@nongnu.org Signed-off-by: Jason Wang Message-Id: <20211111063854.29060-1-jasowang@redhat.com> Reviewed-by: Philippe Mathieu-Daudé Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- hw/virtio/virtio.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index cc69a9b881..939bcbfeb9 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -507,11 +507,9 @@ static void vring_packed_desc_read_flags(VirtIODevice *vdev, MemoryRegionCache *cache, int i) { - address_space_read_cached(cache, - i * sizeof(VRingPackedDesc) + - offsetof(VRingPackedDesc, flags), - flags, sizeof(*flags)); - virtio_tswap16s(vdev, flags); + hwaddr off = i * sizeof(VRingPackedDesc) + offsetof(VRingPackedDesc, flags); + + *flags = virtio_lduw_phys_cached(vdev, cache, off); } static void vring_packed_desc_read(VirtIODevice *vdev, @@ -564,8 +562,7 @@ static void vring_packed_desc_write_flags(VirtIODevice *vdev, { hwaddr off = i * sizeof(VRingPackedDesc) + offsetof(VRingPackedDesc, flags); - virtio_tswap16s(vdev, &desc->flags); - address_space_write_cached(cache, off, &desc->flags, sizeof(desc->flags)); + virtio_stw_phys_cached(vdev, cache, off, desc->flags); address_space_cache_invalidate(cache, off, sizeof(desc->flags)); }