[PATCH v2] drm/amdgpu: Fix VRAM BO swap issue

[Christian König]

Am 22.09.22 um 17:26 schrieb Arunpravin Paneer Selvam:
> DRM buddy manager allocates the contiguous memory requests in
> a single block or multiple blocks. So for the ttm move operation
> (incase of low vram memory) we should consider all the blocks to
> compute the total memory size which compared with the struct
> ttm_resource num_pages in order to verify that the blocks are
> contiguous for the eviction process.
>
> v2: Added a Fixes tag
>
> Fixes: c9cad937c0c5 ("drm/amdgpu: add drm buddy support to amdgpu")
> Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam at amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 20 ++++++++++++++++++--
>   1 file changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index b1c455329023..b1223c8e30c9 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -426,6 +426,7 @@ static bool amdgpu_mem_visible(struct amdgpu_device *adev,
>   {
>   	uint64_t mem_size = (u64)mem->num_pages << PAGE_SHIFT;
>   	struct amdgpu_res_cursor cursor;
> +	u64 start, size, total_size = 0;
>   
>   	if (mem->mem_type == TTM_PL_SYSTEM ||
>   	    mem->mem_type == TTM_PL_TT)
> @@ -435,8 +436,23 @@ static bool amdgpu_mem_visible(struct amdgpu_device *adev,
>   
>   	amdgpu_res_first(mem, 0, mem_size, &cursor);
>   
> -	/* ttm_resource_ioremap only supports contiguous memory */
> -	if (cursor.size != mem_size)
> +	do {
> +		start = cursor.start;
> +		size = cursor.size;
> +
> +		total_size += size;
> +
> +		amdgpu_res_next(&cursor, cursor.size);
> +
> +		if (!cursor.remaining)
> +			break;
> +
> +		/* ttm_resource_ioremap only supports contiguous memory */
> +		if (start + size != cursor.start)
> +			return false;
> +	} while (1);
> +
> +	if (total_size != mem_size)
>   		return false;

I would completely drop this extra check.

>   	return cursor.start + cursor.size <= adev->gmc.visible_vram_size;

Instead of this you should be able to do all of this in one go.

Something like this here should work:

amdgpu_res_first(...
end = cursor.start + cursor.size;
do (
     amdgpu_res_next(....
     if (end != cursor.start)
         return false;
     end = cursor.start + cursor.size;
} while (cursor.remaining);
return end <= visible_vram_size;

Saves a bit of extra calculations and variables.

Regards,
Christian.