linux-kernel - Re: [PATCH 2/2] drm/msm: Restore error return on invalid fence

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Date:   Tue, 16 Nov 2021 11:28:57 +0530
From:   Akhil P Oommen <akhilpo@...eaurora.org>
To:     Rob Clark <robdclark@...il.com>
Cc:     Rob Clark <robdclark@...omium.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        David Airlie <airlied@...ux.ie>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        "moderated list:DMA BUFFER SHARING FRAMEWORK" 
        <linaro-mm-sig@...ts.linaro.org>, Sean Paul <sean@...rly.run>,
        Christian König <christian.koenig@....com>,
        "open list:DMA BUFFER SHARING FRAMEWORK" 
        <linux-media@...r.kernel.org>
Subject: Re: [PATCH 2/2] drm/msm: Restore error return on invalid fence

On 11/15/2021 10:26 PM, Rob Clark wrote:
> On Mon, Nov 15, 2021 at 6:43 AM Akhil P Oommen <akhilpo@...eaurora.org> wrote:
>>
>> On 11/12/2021 12:54 AM, Rob Clark wrote:
>>> From: Rob Clark <robdclark@...omium.org>
>>>
>>> When converting to use an idr to map userspace fence seqno values back
>>> to a dma_fence, we lost the error return when userspace passes seqno
>>> that is larger than the last submitted fence.  Restore this check.
>>>
>>> Reported-by: Akhil P Oommen <akhilpo@...eaurora.org>
>>> Fixes: a61acbbe9cf8 ("drm/msm: Track "seqno" fences by idr")
>>> Signed-off-by: Rob Clark <robdclark@...omium.org>
>>> ---
>>> Note: I will rebase "drm/msm: Handle fence rollover" on top of this,
>>> to simplify backporting this patch to stable kernels
>>>
>>>    drivers/gpu/drm/msm/msm_drv.c        | 6 ++++++
>>>    drivers/gpu/drm/msm/msm_gem_submit.c | 1 +
>>>    drivers/gpu/drm/msm/msm_gpu.h        | 3 +++
>>>    3 files changed, 10 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
>>> index cb14d997c174..56500eb5219e 100644
>>> --- a/drivers/gpu/drm/msm/msm_drv.c
>>> +++ b/drivers/gpu/drm/msm/msm_drv.c
>>> @@ -967,6 +967,12 @@ static int wait_fence(struct msm_gpu_submitqueue *queue, uint32_t fence_id,
>>>        struct dma_fence *fence;
>>>        int ret;
>>>
>>> +     if (fence_id > queue->last_fence) {
>>
>> But fence_id can wrap around and then this check won't be valid.
> 
> that is correct, but see my note about rebasing "drm/msm: Handle fence
> rollover" on top of this patch, so this patch could be more easily
> cherry-picked to stable/lts branches
> 
> BR,
> -R

Missed that. Thanks.

Reviewed-by: Akhil P Oommen <akhilpo@...eaurora.org>

-Akhil.
> 
>> -Akhil.
>>
>>> +             DRM_ERROR_RATELIMITED("waiting on invalid fence: %u (of %u)\n",
>>> +                                   fence_id, queue->last_fence);
>>> +             return -EINVAL;
>>> +     }
>>> +
>>>        /*
>>>         * Map submitqueue scoped "seqno" (which is actually an idr key)
>>>         * back to underlying dma-fence
>>> diff --git a/drivers/gpu/drm/msm/msm_gem_submit.c b/drivers/gpu/drm/msm/msm_gem_submit.c
>>> index 151d19e4453c..a38f23be497d 100644
>>> --- a/drivers/gpu/drm/msm/msm_gem_submit.c
>>> +++ b/drivers/gpu/drm/msm/msm_gem_submit.c
>>> @@ -911,6 +911,7 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data,
>>>        drm_sched_entity_push_job(&submit->base, queue->entity);
>>>
>>>        args->fence = submit->fence_id;
>>> +     queue->last_fence = submit->fence_id;
>>>
>>>        msm_reset_syncobjs(syncobjs_to_reset, args->nr_in_syncobjs);
>>>        msm_process_post_deps(post_deps, args->nr_out_syncobjs,
>>> diff --git a/drivers/gpu/drm/msm/msm_gpu.h b/drivers/gpu/drm/msm/msm_gpu.h
>>> index bd4e0024033e..e73a5bb03544 100644
>>> --- a/drivers/gpu/drm/msm/msm_gpu.h
>>> +++ b/drivers/gpu/drm/msm/msm_gpu.h
>>> @@ -376,6 +376,8 @@ static inline int msm_gpu_convert_priority(struct msm_gpu *gpu, int prio,
>>>     * @ring_nr:   the ringbuffer used by this submitqueue, which is determined
>>>     *             by the submitqueue's priority
>>>     * @faults:    the number of GPU hangs associated with this submitqueue
>>> + * @last_fence: the sequence number of the last allocated fence (for error
>>> + *             checking)
>>>     * @ctx:       the per-drm_file context associated with the submitqueue (ie.
>>>     *             which set of pgtables do submits jobs associated with the
>>>     *             submitqueue use)
>>> @@ -391,6 +393,7 @@ struct msm_gpu_submitqueue {
>>>        u32 flags;
>>>        u32 ring_nr;
>>>        int faults;
>>> +     uint32_t last_fence;
>>>        struct msm_file_private *ctx;
>>>        struct list_head node;
>>>        struct idr fence_idr;
>>>
>>