From 9ff3a5c88e1f1ab17a31402b96d45abe14aab9d7 Mon Sep 17 00:00:00 2001
From: David Riley <davidriley@chromium.org>
Date: Mon, 10 Jun 2019 14:18:10 -0700
Subject: [PATCH] drm/virtio: Add memory barriers for capset cache.
Git-commit: 9ff3a5c88e1f1ab17a31402b96d45abe14aab9d7
Patch-mainline: v5.3-rc1
References: bsc#1051510

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>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/virtio/virtgpu_ioctl.c |    3 +++
 drivers/gpu/drm/virtio/virtgpu_vq.c    |    2 ++
 2 files changed, 5 insertions(+)

--- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
+++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
@@ -521,6 +521,9 @@ static int virtio_gpu_get_caps_ioctl(str
 	if (!ret)
 		return -EBUSY;
 
+	/* is_valid check must proceed before copy of the cache entry. */
+	smp_rmb();
+
 	ptr = cache_ent->caps_cache;
 
 copy_exit:
--- a/drivers/gpu/drm/virtio/virtgpu_vq.c
+++ b/drivers/gpu/drm/virtio/virtgpu_vq.c
@@ -585,6 +585,8 @@ static void virtio_gpu_cmd_capset_cb(str
 		    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;
 		}