linux-kernel - Re: [PATCH v4 2/4] drm/amdgpu: Rework coredump to use memory dynamically

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Message-ID: <48c9521c-88f5-4975-8bf0-85ac42431a36@igalia.com>
Date:   Thu, 17 Aug 2023 12:38:17 -0300
From:   André Almeida <andrealmeid@...lia.com>
To:     Shashank Sharma <shashank.sharma@....com>
Cc:     pierre-eric.pelloux-prayer@....com, amd-gfx@...ts.freedesktop.org,
        'Marek Olšák' <maraeo@...il.com>,
        Timur Kristóf <timur.kristof@...il.com>,
        Samuel Pitoiset <samuel.pitoiset@...il.com>,
        kernel-dev@...lia.com, alexander.deucher@....com,
        christian.koenig@....com, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v4 2/4] drm/amdgpu: Rework coredump to use memory
 dynamically



Em 17/08/2023 12:26, Shashank Sharma escreveu:
> 
> On 17/08/2023 17:17, André Almeida wrote:
>>
>>
>> Em 17/08/2023 12:04, Shashank Sharma escreveu:
>>>
>>> On 17/08/2023 15:45, André Almeida wrote:
>>>> Hi Shashank,
>>>>
>>>> Em 17/08/2023 03:41, Shashank Sharma escreveu:
>>>>> Hello Andre,
>>>>>
>>>>> On 15/08/2023 21:50, André Almeida wrote:
>>>>>> Instead of storing coredump information inside amdgpu_device struct,
>>>>>> move if to a proper separated struct and allocate it dynamically. 
>>>>>> This
>>>>>> will make it easier to further expand the logged information.
>>>>>>
>>>>>> Signed-off-by: André Almeida <andrealmeid@...lia.com>
>>>>>> ---
>>>>>> v4: change kmalloc to kzalloc
>>>>>> ---
>>>>>>   drivers/gpu/drm/amd/amdgpu/amdgpu.h        | 14 +++--
>>>>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 63 
>>>>>> ++++++++++++++--------
>>>>>>   2 files changed, 49 insertions(+), 28 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h 
>>>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>>>>> index 9c6a332261ab..0d560b713948 100644
>>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>>>>> @@ -1088,11 +1088,6 @@ struct amdgpu_device {
>>>>>>       uint32_t *reset_dump_reg_list;
>>>>>>       uint32_t            *reset_dump_reg_value;
>>>>>>       int                             num_regs;
>>>>>> -#ifdef CONFIG_DEV_COREDUMP
>>>>>> -    struct amdgpu_task_info         reset_task_info;
>>>>>> -    bool                            reset_vram_lost;
>>>>>> -    struct timespec64               reset_time;
>>>>>> -#endif
>>>>>>       bool                            scpm_enabled;
>>>>>>       uint32_t                        scpm_status;
>>>>>> @@ -1105,6 +1100,15 @@ struct amdgpu_device {
>>>>>>       uint32_t            aid_mask;
>>>>>>   };
>>>>>> +#ifdef CONFIG_DEV_COREDUMP
>>>>>> +struct amdgpu_coredump_info {
>>>>>> +    struct amdgpu_device        *adev;
>>>>>> +    struct amdgpu_task_info         reset_task_info;
>>>>>> +    struct timespec64               reset_time;
>>>>>> +    bool                            reset_vram_lost;
>>>>>> +};
>>>>>
>>>>> The patch looks good to me in general, but I would recommend 
>>>>> slightly different arrangement and segregation of GPU reset 
>>>>> information.
>>>>>
>>>>> Please consider a higher level structure adev->gpu_reset_info, and 
>>>>> move everything related to reset dump info into that, including 
>>>>> this new coredump_info structure, something like this:
>>>>>
>>>>> struct amdgpu_reset_info {
>>>>>
>>>>>      uint32_t *reset_dump_reg_list;
>>>>>
>>>>>      uint32_t *reset_dump_reg_value;
>>>>>
>>>>>      int num_regs;
>>>>>
>>>>
>>>> Right, I can encapsulate there reset_dump members,
>>>>
>>>>> #ifdef CONFIG_DEV_COREDUMP
>>>>>
>>>>>     struct amdgpu_coredump_info *coredump_info;/* keep this dynamic 
>>>>> allocation */
>>>>
>>>> but we don't need a pointer for amdgpu_coredump_info inside 
>>>> amdgpu_device or inside of amdgpu_device->gpu_reset_info, right?
>>>
>>> I think it would be better if we keep all of the GPU reset related 
>>> data in the same structure, so adev->gpu_reset_info->coredump_info 
>>> sounds about right to me.
>>>
>>
>> But after patch 2/4, we don't need to store a coredump_info pointer 
>> inside adev, this is what I meant. What would be the purpose of having 
>> this pointer? It's freed by amdgpu_devcoredump_free(), so we don't 
>> need to keep track of it.
> 
> Well, actually we are pulling in some 0parallel efforts on enhancing the 
> GPU reset information, and we were planning to use the coredump info for 
> some additional things. So if I have the coredump_info available (like 
> reset_task_info and vram_lost) across a few functions in the driver with 
> adev, it would make my job easy there :).

It seems dangerous to use an object with this limited lifetime to rely 
to read on. If you want to use it you will need to change 
amdgpu_devcoredump_free() to drop a reference or you will need to use it 
statically, which defeats the purpose of this patch. Anyway, I'll add it 
as you requested.

> 
> - Shashank
> 
>>
>>> - Shashank
>>>
>>>>
>>>>>
>>>>> #endif
>>>>>
>>>>> }
>>>>>
>>>>>
>>>>> This will make sure that all the relevant information is at the 
>>>>> same place.
>>>>>
>>>>> - Shashank
>>>>>
>>>>        amdgpu_inc_vram_lost(tmp_adev);