[PATCH v2] drm/amd/display: Reject non-zero src_y and src_x for video planes

[PATCH v2] drm/amd/display: Reject non-zero src_y and src_x for video planes

[Harry Wentland]

[Why]
This hasn't been well tested and leads to complete system hangs on DCN1
based systems, possibly others.

The system hang can be reproduced by gesturing the video on the YouTube
Android app on ChromeOS into full screen.

[How]
Reject atomic commits with non-zero drm_plane_state.src_x or src_y values.

v2:
 - Add code comment describing the reason we're rejecting non-zero
   src_x and src_y
 - Drop gerrit Change-Id
 - Add stable CC
 - Based on amd-staging-drm-next

Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Cc: stable@vger.kernel.org
Cc: nicholas.kazlauskas@amd.com
Cc: amd-gfx@lists.freedesktop.org
Cc: alexander.deucher@amd.com
Cc: Roman.Li@amd.com
Cc: hersenxs.wu@amd.com
Cc: danny.wang@amd.com
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c   | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index be1769d29742..b12469043e6b 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -4089,6 +4089,23 @@ static int fill_dc_scaling_info(const struct drm_plane_state *state,
 	scaling_info->src_rect.x = state->src_x >> 16;
 	scaling_info->src_rect.y = state->src_y >> 16;
 
+	/*
+	 * For reasons we don't (yet) fully understand a non-zero
+	 * src_y coordinate into an NV12 buffer can cause a
+	 * system hang. To avoid hangs (and maybe be overly cautious)
+	 * let's reject both non-zero src_x and src_y.
+	 * 
+	 * We currently know of only one use-case to reproduce a
+	 * scenario with non-zero src_x and src_y for NV12, which
+	 * is to gesture the YouTube Android app into full screen
+	 * on ChromeOS.
+	 */
+	if (state->fb &&
+	    state->fb->format->format == DRM_FORMAT_NV12 &&
+	    (scaling_info->src_rect.x != 0 ||
+	     scaling_info->src_rect.y != 0))
+		return -EINVAL;
+
 	scaling_info->src_rect.width = state->src_w >> 16;
 	if (scaling_info->src_rect.width == 0)
 		return -EINVAL;
-- 
2.31.1

Re: [PATCH v2] drm/amd/display: Reject non-zero src_y and src_x for video planes

[Christian König]

Good that this has been found. Just a curious guess, but have you guys 
checked if the src_x and src_y are a multiple of 2?

Might cause problems to try to access a subsampled surface if the 
coordinates doesn't make much sense.

Anyway patch is Acked-by: Christian König <christian.koenig@amd.com>

Regards,
Christian.

Am 23.04.21 um 16:09 schrieb Harry Wentland:
> [Why]
> This hasn't been well tested and leads to complete system hangs on DCN1
> based systems, possibly others.
>
> The system hang can be reproduced by gesturing the video on the YouTube
> Android app on ChromeOS into full screen.
>
> [How]
> Reject atomic commits with non-zero drm_plane_state.src_x or src_y values.
>
> v2:
>   - Add code comment describing the reason we're rejecting non-zero
>     src_x and src_y
>   - Drop gerrit Change-Id
>   - Add stable CC
>   - Based on amd-staging-drm-next
>
> Signed-off-by: Harry Wentland <harry.wentland@amd.com>
> Cc: stable@vger.kernel.org
> Cc: nicholas.kazlauskas@amd.com
> Cc: amd-gfx@lists.freedesktop.org
> Cc: alexander.deucher@amd.com
> Cc: Roman.Li@amd.com
> Cc: hersenxs.wu@amd.com
> Cc: danny.wang@amd.com
> Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
> ---
>   .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c   | 17 +++++++++++++++++
>   1 file changed, 17 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index be1769d29742..b12469043e6b 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -4089,6 +4089,23 @@ static int fill_dc_scaling_info(const struct drm_plane_state *state,
>   	scaling_info->src_rect.x = state->src_x >> 16;
>   	scaling_info->src_rect.y = state->src_y >> 16;
>   
> +	/*
> +	 * For reasons we don't (yet) fully understand a non-zero
> +	 * src_y coordinate into an NV12 buffer can cause a
> +	 * system hang. To avoid hangs (and maybe be overly cautious)
> +	 * let's reject both non-zero src_x and src_y.
> +	 *
> +	 * We currently know of only one use-case to reproduce a
> +	 * scenario with non-zero src_x and src_y for NV12, which
> +	 * is to gesture the YouTube Android app into full screen
> +	 * on ChromeOS.
> +	 */
> +	if (state->fb &&
> +	    state->fb->format->format == DRM_FORMAT_NV12 &&
> +	    (scaling_info->src_rect.x != 0 ||
> +	     scaling_info->src_rect.y != 0))
> +		return -EINVAL;
> +
>   	scaling_info->src_rect.width = state->src_w >> 16;
>   	if (scaling_info->src_rect.width == 0)
>   		return -EINVAL;

Re: [PATCH v2] drm/amd/display: Reject non-zero src_y and src_x for video planes

[Harry Wentland]

On 2021-04-23 10:18 a.m., Christian König wrote:
> Good that this has been found. Just a curious guess, but have you guys 
> checked if the src_x and src_y are a multiple of 2?
> 

That was one of my first guesses but I still observed the hang after
forcing src_x and src_y to be multiples of 2.

> Might cause problems to try to access a subsampled surface if the 
> coordinates doesn't make much sense.
> 
> Anyway patch is Acked-by: Christian König <christian.koenig@amd.com>
> 

Thanks,
Harry

> Regards,
> Christian.
> 
> Am 23.04.21 um 16:09 schrieb Harry Wentland:
>> [Why]
>> This hasn't been well tested and leads to complete system hangs on DCN1
>> based systems, possibly others.
>>
>> The system hang can be reproduced by gesturing the video on the YouTube
>> Android app on ChromeOS into full screen.
>>
>> [How]
>> Reject atomic commits with non-zero drm_plane_state.src_x or src_y 
>> values.
>>
>> v2:
>>   - Add code comment describing the reason we're rejecting non-zero
>>     src_x and src_y
>>   - Drop gerrit Change-Id
>>   - Add stable CC
>>   - Based on amd-staging-drm-next
>>
>> Signed-off-by: Harry Wentland <harry.wentland@amd.com>
>> Cc: stable@vger.kernel.org
>> Cc: nicholas.kazlauskas@amd.com
>> Cc: amd-gfx@lists.freedesktop.org
>> Cc: alexander.deucher@amd.com
>> Cc: Roman.Li@amd.com
>> Cc: hersenxs.wu@amd.com
>> Cc: danny.wang@amd.com
>> Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
>> ---
>>   .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c   | 17 +++++++++++++++++
>>   1 file changed, 17 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c 
>> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> index be1769d29742..b12469043e6b 100644
>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> @@ -4089,6 +4089,23 @@ static int fill_dc_scaling_info(const struct 
>> drm_plane_state *state,
>>       scaling_info->src_rect.x = state->src_x >> 16;
>>       scaling_info->src_rect.y = state->src_y >> 16;
>> +    /*
>> +     * For reasons we don't (yet) fully understand a non-zero
>> +     * src_y coordinate into an NV12 buffer can cause a
>> +     * system hang. To avoid hangs (and maybe be overly cautious)
>> +     * let's reject both non-zero src_x and src_y.
>> +     *
>> +     * We currently know of only one use-case to reproduce a
>> +     * scenario with non-zero src_x and src_y for NV12, which
>> +     * is to gesture the YouTube Android app into full screen
>> +     * on ChromeOS.
>> +     */
>> +    if (state->fb &&
>> +        state->fb->format->format == DRM_FORMAT_NV12 &&
>> +        (scaling_info->src_rect.x != 0 ||
>> +         scaling_info->src_rect.y != 0))
>> +        return -EINVAL;
>> +
>>       scaling_info->src_rect.width = state->src_w >> 16;
>>       if (scaling_info->src_rect.width == 0)
>>           return -EINVAL;
>