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

[Melissa Wen]

On 19/11/2024 14:04, Mohamed, Zaeem wrote:
> [AMD Official Use Only - AMD Internal Distribution Only]
>
> Hi Melissa,
>
> Could you share your configuration that experienced this pagefault?
Hi Zaeem,

Page fault was experienced by one of the reporter here:
https://gitlab.freedesktop.org/drm/amd/-/issues/3693#note_2659173
^ You can find all details (dtn_log and drm_info) in this issue from 
that comment.

As I mentioned, I don't have the proper hardware and environment to 
reproduce their issues.

Thanks,

Melissa
>
> Thanks,
> Zaeem
>
> -----Original Message-----
> From: Melissa Wen <mwen at igalia.com>
> Sent: Monday, November 18, 2024 7:52 AM
> To: Limonciello, Mario <Mario.Limonciello at amd.com>; Mohamed, Zaeem <Zaeem.Mohamed at amd.com>; amd-gfx at lists.freedesktop.org
> Subject: Re: [PATCH] SWDEV-476969 - dm/amdgpu: Fail dm_atomic_check if cursor overlay is required at MAX_SURFACES
>
>
>
>
> 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@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,
>
> 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) &&