Re: [PATCH v2] drm/amdgpu: Fix size validation for non-exclusive domains

["Christian König" <christian.koenig@amd.com>]

Am 13.12.22 um 00:44 schrieb Luben Tuikov:
> On 2022-12-12 14:19, Christian König wrote:
>> Am 12.12.22 um 18:48 schrieb Luben Tuikov:
>>> Fix amdgpu_bo_validate_size() to check whether the TTM domain manager for the
>>> requested memory exists, and to allow for non-exclusive domain allocations, as
>>> there would be if the domain is a mask, e.g. AMDGPU_GEM_DOMAIN_VRAM |
>>> AMDGPU_GEM_DOMAIN_GTT.
>>>
>>> Cc: Alex Deucher <Alexander.Deucher@amd.com>
>>> Cc: Christian König <christian.koenig@amd.com>
>>> Signed-off-by: Luben Tuikov <luben.tuikov@amd.com>
>>> ---
>>>    drivers/gpu/drm/amd/amdgpu/amdgpu_object.c | 19 +++++++------------
>>>    1 file changed, 7 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>>> index fd3ab4b5e5bb1f..e0f103f0ec2178 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
>>> @@ -448,31 +448,26 @@ static bool amdgpu_bo_validate_size(struct amdgpu_device *adev,
>>>    
>>>    	/*
>>>    	 * If GTT is part of requested domains the check must succeed to
>>> -	 * allow fall back to GTT
>>> +	 * allow fall back to GTT.
>>> +	 *
>>> +	 * Note that allocations can request from either domain. For
>>> +	 * this reason, check either in non-exclusive way, and if
>>> +	 * neither satisfies, fail the validation.
>> That's not correct, the original logic was completely intentional.
>>
>> If both VRAM and GTT are specified it's valid if the size fits only into
>> GTT.
> Given that this patch fixes a kernel oops, should this patch then fail the validation,
> i.e. return false?

It should be sufficient if a BO fits into the GTT domain for size 
validation. If we haven't initialized the GTT domain and end up here we 
should probably just ignore it.

>
> This would then fail, in amdgpu_ttm_reserve_tmr():
>
> 	ret = amdgpu_bo_create_kernel_at(adev,
> 				adev->gmc.real_vram_size - adev->mman.discovery_tmr_size,
> 				adev->mman.discovery_tmr_size,
> 				AMDGPU_GEM_DOMAIN_VRAM |
> 				AMDGPU_GEM_DOMAIN_GTT,

As I said before using amdgpu_bo_create_kernel_at() with VRAM|GTT 
doesn't make any sense at all. We should probably drop the domain 
parameter altogether.

Regards,
Christian.

> 				&adev->mman.discovery_memory,
> 				NULL);
>
> Regards,
> Luben
>