Sasha Levin
2019-Jul-19 04:13 UTC
[PATCH AUTOSEL 4.4 10/35] drm/virtio: Add memory barriers for capset cache.
From: David Riley <davidriley at chromium.org>
[ 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 at chromium.org>
Link:
http://patchwork.freedesktop.org/patch/msgid/20190610211810.253227-5-davidriley
at chromium.org
Signed-off-by: Gerd Hoffmann <kraxel at redhat.com>
Signed-off-by: Sasha Levin <sashal at kernel.org>
---
drivers/gpu/drm/virtio/virtgpu_ioctl.c | 3 +++
drivers/gpu/drm/virtio/virtgpu_vq.c | 2 ++
2 files changed, 5 insertions(+)
diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
index 6296e9f270ca..0b8f8c10f2ed 100644
--- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
+++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
@@ -535,6 +535,9 @@ static int virtio_gpu_get_caps_ioctl(struct drm_device *dev,
ret = wait_event_timeout(vgdev->resp_wq,
atomic_read(&cache_ent->is_valid), 5 * HZ);
+ /* 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 52436b3c01bb..a1b3ea1ccb65 100644
--- a/drivers/gpu/drm/virtio/virtgpu_vq.c
+++ b/drivers/gpu/drm/virtio/virtgpu_vq.c
@@ -618,6 +618,8 @@ 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;
}
--
2.20.1