[PATCH] drm/amdkfd: Get prange->offset after svm_range_vram_node_new

[Felix Kuehling]

On 2023-03-08 02:45, Xiaogang.Chen wrote:
> From: Xiaogang Chen <xiaogang.chen at amd.com>
>
> During miration to vram prange->offset is valid after vram buffer is located,
> either use old one or allocate a new one. Move svm_range_vram_node_new before migrate
> for each vma to get valid prange->offset.
>
> Signed-off-by: Xiaogang Chen <Xiaogang.Chen at amd.com>

I'd  prefer to keep svm_range_vram_node_new in svm_migrate_copy_to_vram. 
Logically the memory allocation should be after migrate_vma_setup. If 
migrate_vma_setup finds that there is nothing to migrate, we should not 
allocate any memory.

Does this fix a real issue, or is this a theoretical fix? I think it 
should probably work correctly without this patch. 
svm_range_vram_node_new sets prange->offset to 0. If no VRAM was 
previously allocated, it should already be 0, so nothing changes. Maybe 
we just need a fix to set prange->offset = 0 in svm_range_vram_node_free.

Regards,
   Felix


> ---
>   drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 12 ++++++------
>   1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> index fd54a00e7229..15791490c23e 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> @@ -310,12 +310,6 @@ svm_migrate_copy_to_vram(struct amdgpu_device *adev, struct svm_range *prange,
>   	src = scratch;
>   	dst = (uint64_t *)(scratch + npages);
>   
> -	r = svm_range_vram_node_new(adev, prange, true);
> -	if (r) {
> -		dev_dbg(adev->dev, "fail %d to alloc vram\n", r);
> -		goto out;
> -	}
> -
>   	amdgpu_res_first(prange->ttm_res, ttm_res_offset,
>   			 npages << PAGE_SHIFT, &cursor);
>   	for (i = j = 0; i < npages; i++) {
> @@ -525,6 +519,12 @@ svm_migrate_ram_to_vram(struct svm_range *prange, uint32_t best_loc,
>   
>   	start = prange->start << PAGE_SHIFT;
>   	end = (prange->last + 1) << PAGE_SHIFT;
> +
> +	r = svm_range_vram_node_new(adev, prange, true);
> +	if (r) {
> +		dev_dbg(adev->dev, "fail %d to alloc vram\n", r);
> +		return r;
> +	}
>   	ttm_res_offset = prange->offset << PAGE_SHIFT;
>   
>   	for (addr = start; addr < end;) {