[PATCH] drm/amdkfd: Page aligned VRAM reserve size

[Felix Kuehling]

Am 2023-01-09 um 19:01 schrieb Philip Yang:
> Use page aligned size to reserve VRAM usage because page aligned TTM BO
> size is used to unreserve VRAM usage, otherwise this cause vram_used
> accounting unbalanced.
>
> Change vram_used definition type to int64_t to be able to trigger
> WARN_ONCE(adev && adev->kfd.vram_used < 0, "..."), to help debug the
> accouting issue with warning and backtrace.
>
> Signed-off-by: Philip Yang <Philip.Yang at amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h       | 2 +-
>   drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c | 2 +-
>   2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h
> index fb41869e357a..333780491867 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h
> @@ -97,7 +97,7 @@ struct amdgpu_amdkfd_fence {
>   
>   struct amdgpu_kfd_dev {
>   	struct kfd_dev *dev;
> -	uint64_t vram_used;
> +	int64_t vram_used;
>   	uint64_t vram_used_aligned;
>   	bool init_complete;
>   	struct work_struct reset_work;
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> index 2a118669d0e3..f23d94e57762 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> @@ -151,7 +151,7 @@ int amdgpu_amdkfd_reserve_mem_limit(struct amdgpu_device *adev,
>   		 * to avoid fragmentation caused by 4K allocations in the tail
>   		 * 2M BO chunk.
>   		 */
> -		vram_needed = size;
> +		vram_needed = PAGE_ALIGN(size);

This only solves part of the problem. size is used in other places in 
this function that should all use the page-aligned size. I think we 
should do the page-alignment at a much higher level, in 
kfd_ioctl_alloc_memory_of_gpu. That way all the kernel code can safely 
assume that buffer sizes are page aligned, and we avoid future surprises.

Regards,
   Felix


>   	} else if (alloc_flag & KFD_IOC_ALLOC_MEM_FLAGS_USERPTR) {
>   		system_mem_needed = size;
>   	} else if (!(alloc_flag &