[PATCH] SWDEV-476969 - dm/amdgpu: Fail dm_atomic_check if cursor overlay is required at MAX_SURFACES

[Mario Limonciello]

On 11/18/2024 06:52, Melissa Wen wrote:
> 
> 
> 
> On 14/11/2024 16:04, Mario Limonciello wrote:
>> Although it's really useful information for AMD people, the Jira 
>> shouldn't be in the "title" of the commit message.
>>
>> "If" we want to get into the habit of including this information for 
>> display code we should come up with a prescriptive field that goes 
>> into the commit message during promotion and it should be part of all 
>> patches in the promotion that have it.
>>
>> Something like this:
>>
>> AMD-Jira: SWDEV-476969
>>
>> Probably need to align that with other stakeholders though before 
>> starting that way.
>>
>> On 11/14/2024 08:37, Zaeem Mohamed wrote:
>>> [why]
>>> Prevent index-out-of-bounds due to requiring cursor overlay when
>>> plane_count is MAX_SURFACES.
>>>
>>> [how]
>>> Bounds check on plane_count when requiring overlay cursor.
>>>
>>
>> Any link to failing bugs or anything like that you can include?
> Hi Mario,
> 
> About this question, these are the related issues:
> - Link: https://gitlab.freedesktop.org/drm/amd/-/issues/3693
> - Link: https://gitlab.freedesktop.org/drm/amd/-/issues/3594
> 
> You can find more details in previous iterations related to this bug:
> - https://lore.kernel.org/amd-gfx/575d66c7-e77d-42ea- 
> acbf-412d6e508a0b at igalia.com/
> - https://lore.kernel.org/amd-gfx/20240925154324.348774-1-mwen@igalia.com/
>>
>>> Co-developed-by: Melissa Wen <mwen at igalia.com>
>>> Signed-off-by: Zaeem Mohamed <zaeem.mohamed at amd.com>
>>
>> You're missing Melisaa's SoB for a co-developed patch.
>> IIRC this should fail checkpatch.
> I already mentioned before, I don't think I actually co-dev this code, 
> so Zaeem can remove it in the next iteration.
> 
> ---
> 
> BTW, about the implementation:
> 
> As I don't have the proper environment, I asked reporters to check this 
> patch up and it doesn't help prevent interface freeze.
> It seems to prevent the out of bounds bug but is causing a page fault now:
> 
> kernel: BUG: unable to handle page fault for address: 000000000174e354
> 
>  From their feedback, I found curious that MAX_SURFACES -> 4 prevents 
> the freeze but not completely solve the problem.
> MAX_SURFACES -> 6 solves it, what let me consider that the MAX_SURFACES 
> vs MAX_SURFACE_NUM vs MAX_PLANE mismatch might be related.
> I'm going to analyzing the logs but you can find more details here: 
> https://gitlab.freedesktop.org/drm/amd/-/issues/3693#note_2658994
> 
> BR,

Got it, thanks for the context!

Zaeem, please add links to these in your next iteration of the patch.

> 
> Melissa Wen
>>
>>> ---
>>>   amdgpu_dm/amdgpu_dm.c | 10 +++++++++-
>>>   1 file changed, 9 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/amdgpu_dm/amdgpu_dm.c b/amdgpu_dm/amdgpu_dm.c
>>> index 97e0a1bbba..964497c613 100644
>>> --- a/amdgpu_dm/amdgpu_dm.c
>>> +++ b/amdgpu_dm/amdgpu_dm.c
>>> @@ -11821,8 +11821,16 @@ static int amdgpu_dm_atomic_check(struct 
>>> drm_device *dev,
>>>             /* Overlay cusor not subject to native cursor 
>>> restrictions */
>>>           dm_new_crtc_state = to_dm_crtc_state(new_crtc_state);
>>> -        if (dm_new_crtc_state->cursor_mode == DM_CURSOR_OVERLAY_MODE)
>>> +        if (dm_new_crtc_state->cursor_mode == DM_CURSOR_OVERLAY_MODE) {
>>> +            if (dc->current_state->stream_status->plane_count > 
>>> MAX_SURFACES) {
>>> +                drm_dbg_driver(crtc->dev,
>>> +                       "Can't enable cursor plane with %d planes\n", 
>>> MAX_SURFACES);
>>> +                ret = -EINVAL;
>>> +                goto fail;
>>> +            }
>>> +
>>>               continue;
>>> +        }
>>>             /* Check if rotation or scaling is enabled on DCN401 */
>>>           if ((drm_plane_mask(crtc->cursor) & new_crtc_state- 
>>> >plane_mask) &&
>>
>