Nouveau - Sep 2023 - [PATCH] drm/nouveau: fence: fix type cast warning in nouveau_fence_emit()

Fix the following warning.

  drivers/gpu/drm/nouveau/nouveau_fence.c:210:45: sparse: sparse:
  incorrect type in initializer (different address spaces)
  @@     expected struct nouveau_channel *chan
  @@     got struct nouveau_channel [noderef] __rcu *channel

We're just about to emit the fence, there is nothing to protect against
yet, hence it is safe to just cast __rcu away.

Reported-by: kernel test robot <lkp at intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202309140340.BwKXzaDx-lkp at
intel.com/
Fixes: 978474dc8278 ("drm/nouveau: fence: fix undefined fence state after
emit")
Signed-off-by: Danilo Krummrich <dakr at redhat.com>
---
 drivers/gpu/drm/nouveau/nouveau_fence.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_fence.c
b/drivers/gpu/drm/nouveau/nouveau_fence.c
index 61d9e70da9fd..ca762ea55413 100644
--- a/drivers/gpu/drm/nouveau/nouveau_fence.c
+++ b/drivers/gpu/drm/nouveau/nouveau_fence.c
@@ -207,7 +207,7 @@ nouveau_fence_context_new(struct nouveau_channel *chan,
struct nouveau_fence_cha
 int
 nouveau_fence_emit(struct nouveau_fence *fence)
 {
-	struct nouveau_channel *chan = fence->channel;
+	struct nouveau_channel *chan = unrcu_pointer(fence->channel);
 	struct nouveau_fence_chan *fctx = chan->fence;
 	struct nouveau_fence_priv *priv = (void*)chan->drm->fence;
 	int ret;
-- 
2.41.0

On Sat, 16 Sept 2023 at 11:15, Danilo Krummrich <dakr at redhat.com>
wrote:
>
> Fix the following warning.
>
>   drivers/gpu/drm/nouveau/nouveau_fence.c:210:45: sparse: sparse:
>   incorrect type in initializer (different address spaces)
>   @@     expected struct nouveau_channel *chan
>   @@     got struct nouveau_channel [noderef] __rcu *channel
Reviewed-by: Dave Airlie <airlied at redhat.com>
>
> We're just about to emit the fence, there is nothing to protect against
> yet, hence it is safe to just cast __rcu away.
>
> Reported-by: kernel test robot <lkp at intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202309140340.BwKXzaDx-lkp at
intel.com/
> Fixes: 978474dc8278 ("drm/nouveau: fence: fix undefined fence state
after emit")
> Signed-off-by: Danilo Krummrich <dakr at redhat.com>
> ---
>  drivers/gpu/drm/nouveau/nouveau_fence.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nouveau_fence.c
b/drivers/gpu/drm/nouveau/nouveau_fence.c
> index 61d9e70da9fd..ca762ea55413 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_fence.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_fence.c
> @@ -207,7 +207,7 @@ nouveau_fence_context_new(struct nouveau_channel *chan,
struct nouveau_fence_cha
>  int
>  nouveau_fence_emit(struct nouveau_fence *fence)
>  {
> -       struct nouveau_channel *chan = fence->channel;
> +       struct nouveau_channel *chan = unrcu_pointer(fence->channel);
>         struct nouveau_fence_chan *fctx = chan->fence;
>         struct nouveau_fence_priv *priv = (void*)chan->drm->fence;
>         int ret;
> --
> 2.41.0
>

Reviewed-by: Lyude Paul <lyude at redhat.com>

On Sat, 2023-09-16 at 03:14 +0200, Danilo Krummrich
wrote:
> Fix the following warning.
> 
>   drivers/gpu/drm/nouveau/nouveau_fence.c:210:45: sparse: sparse:
>   incorrect type in initializer (different address spaces)
>   @@     expected struct nouveau_channel *chan
>   @@     got struct nouveau_channel [noderef] __rcu *channel
> 
> We're just about to emit the fence, there is nothing to protect against
> yet, hence it is safe to just cast __rcu away.
> 
> Reported-by: kernel test robot <lkp at intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202309140340.BwKXzaDx-lkp at
intel.com/
> Fixes: 978474dc8278 ("drm/nouveau: fence: fix undefined fence state
after emit")
> Signed-off-by: Danilo Krummrich <dakr at redhat.com>
> ---
>  drivers/gpu/drm/nouveau/nouveau_fence.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/nouveau_fence.c
b/drivers/gpu/drm/nouveau/nouveau_fence.c
> index 61d9e70da9fd..ca762ea55413 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_fence.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_fence.c
> @@ -207,7 +207,7 @@ nouveau_fence_context_new(struct nouveau_channel *chan,
struct nouveau_fence_cha
>  int
>  nouveau_fence_emit(struct nouveau_fence *fence)
>  {
> -	struct nouveau_channel *chan = fence->channel;
> +	struct nouveau_channel *chan = unrcu_pointer(fence->channel);
>  	struct nouveau_fence_chan *fctx = chan->fence;
>  	struct nouveau_fence_priv *priv = (void*)chan->drm->fence;
>  	int ret;
-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat