[PATCH 1/2] drm/amdgpu: use CPU to update VM during GPU reset

[Yu, Lang]

[AMD Official Use Only - General]

>-----Original Message-----
>From: Koenig, Christian <Christian.Koenig at amd.com>
>Sent: Friday, March 29, 2024 7:08 PM
>To: Yu, Lang <Lang.Yu at amd.com>; amd-gfx at lists.freedesktop.org
>Cc: Deucher, Alexander <Alexander.Deucher at amd.com>
>Subject: Re: [PATCH 1/2] drm/amdgpu: use CPU to update VM during GPU
>reset
>
>Am 25.03.24 um 06:35 schrieb Lang Yu:
>> drm sched is stopped and SDMA mode is not available, while CPU mode
>> worked well in such a case.
>>
>> Use case,
>> amdgpu_do_asic_reset
>> amdgpu_device_ip_late_init
>> umsch_mm_late_init
>> umsch_mm_test
>> amdgpu_vm_init
>
>Well big NAK to that.
>
>The VM updates should just be scheduled and applied as soon as the GPU
>reset is completed.
>
>The problem is rather that a GPU reset should *never* create a VM to do a
>test. During GPU reset no memory allocation whatsoever is allowed.

But user space can still create a VM via open("/dev/dri/card0", ...) during GPU reset,
driver doesn't prevent user space from doing that. So is this reasonable? Thanks.

Regards,
Lang

>That's why we only do IB and ring tests with a pre-allocated memory pool
>during a GPU reset.
>
>If the umsch_mm_test abuses the VM tests like this then please remove that
>code immediately.
>
>Regards,
>Christian.
>
>>
>> Signed-off-by: Lang Yu <Lang.Yu at amd.com>
>> ---
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>> index 8af3f0fd3073..af53f9cfcc40 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>> @@ -2404,8 +2404,8 @@ int amdgpu_vm_init(struct amdgpu_device
>*adev,
>> struct amdgpu_vm *vm,
>>
>>      vm->is_compute_context = false;
>>
>> -    vm->use_cpu_for_update = !!(adev->vm_manager.vm_update_mode
>&
>> -                                AMDGPU_VM_USE_CPU_FOR_GFX);
>> +    vm->use_cpu_for_update = !!(amdgpu_in_reset(adev) ||
>> +            adev->vm_manager.vm_update_mode &
>AMDGPU_VM_USE_CPU_FOR_GFX);
>>
>>      DRM_DEBUG_DRIVER("VM update mode is %s\n",
>>                       vm->use_cpu_for_update ? "CPU" : "SDMA");