linux-kernel - Re: [PATCH] drm/msm: skip re-emitting IBs for unusable VMs

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Message-ID: <9f94c6d7-7b39-455c-83d1-81c694672775@oss.qualcomm.com>
Date: Mon, 18 Aug 2025 19:36:52 +0530
From: Akhil P Oommen <akhilpo@....qualcomm.com>
To: rob.clark@....qualcomm.com, Antonino Maniscalco <antomani103@...il.com>
Cc: Sean Paul <sean@...rly.run>, Konrad Dybcio <konradybcio@...nel.org>,
        Dmitry Baryshkov <lumag@...nel.org>,
        Abhinav Kumar
 <abhinav.kumar@...ux.dev>,
        Jessica Zhang <jessica.zhang@....qualcomm.com>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/msm: skip re-emitting IBs for unusable VMs

On 8/18/2025 6:48 PM, Rob Clark wrote:
> On Mon, Aug 18, 2025 at 5:10 AM Akhil P Oommen <akhilpo@....qualcomm.com> wrote:
>>
>> On 8/13/2025 6:34 PM, Antonino Maniscalco wrote:
>>> When a VM is marked as an usuable we disallow new submissions from it,
>>> however submissions that where already scheduled on the ring would still
>>> be re-sent.
>>>
>>> Since this can lead to further hangs, avoid emitting the actual IBs.
>>>
>>> Fixes: 6a4d287a1ae6 ("drm/msm: Mark VM as unusable on GPU hangs")
>>> Signed-off-by: Antonino Maniscalco <antomani103@...il.com>
>>> ---
>>>  drivers/gpu/drm/msm/msm_gpu.c | 9 ++++++++-
>>>  1 file changed, 8 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
>>> index c317b25a8162edba0d594f61427eac4440871b73..e6cd85c810bd2314c8bba53644a622464713b7f2 100644
>>> --- a/drivers/gpu/drm/msm/msm_gpu.c
>>> +++ b/drivers/gpu/drm/msm/msm_gpu.c
>>> @@ -553,8 +553,15 @@ static void recover_worker(struct kthread_work *work)
>>>                       unsigned long flags;
>>>
>>>                       spin_lock_irqsave(&ring->submit_lock, flags);
>>> -                     list_for_each_entry(submit, &ring->submits, node)
>>> +                     list_for_each_entry(submit, &ring->submits, node) {
>>> +                             /*
>>> +                              * If the submit uses an unusable vm make sure
>>> +                              * we don't actually run it
>>> +                              */
>>> +                             if (to_msm_vm(submit->vm)->unusable)
>>> +                                     submit->nr_cmds = 0;
>>
>> Just curious, why not just retire this submit here?
> 
> Because then you'd end up with submits retiring out of order (ie.
> fences on the same timeline signaling out of order)

Yeah, that makes sense.

Reviewed-by: Akhil P Oommen <akhilpo@....qualcomm.com>

-Akhil

> 
> BR,
> -R
> 
>> -Akhil
>>
>>>                               gpu->funcs->submit(gpu, submit);
>>> +                     }
>>>                       spin_unlock_irqrestore(&ring->submit_lock, flags);
>>>               }
>>>       }
>>>
>>> ---
>>> base-commit: 8290d37ad2b087bbcfe65fa5bcaf260e184b250a
>>> change-id: 20250813-unusable_fix_b4-10bde6f3b756
>>>
>>> Best regards,
>>