[PATCH 2/2] drm/amdkfd: add svm_migrate_successful_pages

[Philip Yang]

On 2025-05-28 13:19, James Zhu wrote:
> to get migration pages. When migrating pages from system to vram,
> needn't check bit MIGRATE_PFN_VALID, since the system page could
> be allocated, but not be accessed.

I think the corner case is vram_pages becomes negative value when 
migrating prange from vram to system memory, if the src page is on 
system, src MIGRATE_PFN_MIGRATE set, MIGRATE_PFN_VALID not set, this 
count as successful migrate page by svm_migrate_unsuccessful_page.

As discussed offline, we could check dst MIGRATE_PFN_MIGRATE flag for 
both system to vram or vram to system cases.

Regards,

Philip

>
> Signed-off-by: James Zhu <James.Zhu at amd.com>
> ---
>   drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 25 ++++++++++++------------
>   1 file changed, 13 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> index f0b690d4bb46..131838bf8751 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
> @@ -260,17 +260,20 @@ static void svm_migrate_put_sys_page(unsigned long addr)
>   	put_page(page);
>   }
>   
> -static unsigned long svm_migrate_unsuccessful_pages(struct migrate_vma *migrate)
> +static unsigned long svm_migrate_successful_pages(struct migrate_vma *migrate)
>   {
> -	unsigned long upages = 0;
> +	unsigned long mpages = 0;
>   	unsigned long i;
>   
>   	for (i = 0; i < migrate->npages; i++) {
> -		if (migrate->src[i] & MIGRATE_PFN_VALID &&
> -		    !(migrate->src[i] & MIGRATE_PFN_MIGRATE))
> -			upages++;
> +                if (migrate->flags == MIGRATE_VMA_SELECT_SYSTEM &&
> +			migrate->src[i] & MIGRATE_PFN_MIGRATE)
> +                        mpages++;
> +                 else if (migrate->src[i] & MIGRATE_PFN_VALID &&
> +				migrate->src[i] & MIGRATE_PFN_MIGRATE)
> +                        mpages++;
>   	}
> -	return upages;
> +	return mpages;
>   }
>   
>   static int
> @@ -447,7 +450,7 @@ svm_migrate_vma_to_vram(struct kfd_node *node, struct svm_range *prange,
>   	svm_migrate_copy_done(adev, mfence);
>   	migrate_vma_finalize(&migrate);
>   
> -	mpages = cpages - svm_migrate_unsuccessful_pages(&migrate);
> +	mpages = svm_migrate_successful_pages(&migrate);
>   	pr_debug("successful/cpages/npages 0x%lx/0x%lx/0x%lx\n",
>   			 mpages, cpages, migrate.npages);
>   
> @@ -688,7 +691,6 @@ svm_migrate_vma_to_ram(struct kfd_node *node, struct svm_range *prange,
>   {
>   	struct kfd_process *p = container_of(prange->svms, struct kfd_process, svms);
>   	uint64_t npages = (end - start) >> PAGE_SHIFT;
> -	unsigned long upages = npages;
>   	unsigned long cpages = 0;
>   	unsigned long mpages = 0;
>   	struct amdgpu_device *adev = node->adev;
> @@ -748,9 +750,9 @@ svm_migrate_vma_to_ram(struct kfd_node *node, struct svm_range *prange,
>   				    scratch, npages);
>   	migrate_vma_pages(&migrate);
>   
> -	upages = svm_migrate_unsuccessful_pages(&migrate);
> -	pr_debug("unsuccessful/cpages/npages 0x%lx/0x%lx/0x%lx\n",
> -		 upages, cpages, migrate.npages);
> +	mpages = svm_migrate_successful_pages(&migrate);
> +	pr_debug("successful/cpages/npages 0x%lx/0x%lx/0x%lx\n",
> +		 mpages, cpages, migrate.npages);
>   
>   	svm_migrate_copy_done(adev, mfence);
>   	migrate_vma_finalize(&migrate);
> @@ -764,7 +766,6 @@ svm_migrate_vma_to_ram(struct kfd_node *node, struct svm_range *prange,
>   				    node->id, 0, trigger, r);
>   out:
>   	if (!r && cpages) {
> -		mpages = cpages - upages;
>   		pdd = svm_range_get_pdd_by_node(prange, node);
>   		if (pdd)
>   			WRITE_ONCE(pdd->page_out, pdd->page_out + mpages);