drm/virtio: Add memory barriers for capset cache.

[ Upstream commit 9ff3a5c88e1f1ab17a31402b96d45abe14aab9d7 ]

After data is copied to the cache entry, atomic_set is used indicate
that the data is the entry is valid without appropriate memory barriers.
Similarly the read side was missing the corresponding memory barriers.

Signed-off-by: David Riley <davidriley@chromium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20190610211810.253227-5-davidriley@chromium.org
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
index 949a264985fcc53b8c26935f488793028bc7fe53..19fbffd0f7a39f3f6005fe4866945d7e4dc046aa 100644 (file)
--- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
+++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
@@ -542,6 +542,9 @@ static int virtio_gpu_get_caps_ioctl(struct drm_device *dev,
        if (!ret)
                return -EBUSY;
 
+       /* is_valid check must proceed before copy of the cache entry. */
+       smp_rmb();
+
        ptr = cache_ent->caps_cache;
 
 copy_exit:

diff --git a/drivers/gpu/drm/virtio/virtgpu_vq.c b/drivers/gpu/drm/virtio/virtgpu_vq.c
index 5bb0f0a084e9cb293a8a91030e8a6f9a050eb987..a7684f9c80db51acc17cee1685ea085632b26793 100644 (file)
--- a/drivers/gpu/drm/virtio/virtgpu_vq.c
+++ b/drivers/gpu/drm/virtio/virtgpu_vq.c
@@ -583,6 +583,8 @@ static void virtio_gpu_cmd_capset_cb(struct virtio_gpu_device *vgdev,
                    cache_ent->id == le32_to_cpu(cmd->capset_id)) {
                        memcpy(cache_ent->caps_cache, resp->capset_data,
                               cache_ent->size);
+                       /* Copy must occur before is_valid is signalled. */
+                       smp_wmb();
                        atomic_set(&cache_ent->is_valid, 1);
                        break;
                }