[PATCH] mm: add device coherent vma selection for memory migration

[Alistair Popple]

Thanks for fixing. I'm guessing Andrew will want you to resend this as part of
a new v6 series, but please add:

Reviewed-by: Alistair Popple <apopple at nvidia.com>

On Tuesday, 1 February 2022 6:48:13 AM AEDT Alex Sierra wrote:
> This case is used to migrate pages from device memory, back to system
> memory. Device coherent type memory is cache coherent from device and CPU
> point of view.
> 
> Signed-off-by: Alex Sierra <alex.sierra at amd.com>
> Acked-by: Felix Kuehling <Felix.Kuehling at amd.com>
> ---
> v2:
> condition added when migrations from device coherent pages.
> ---
>  include/linux/migrate.h |  1 +
>  mm/migrate.c            | 12 +++++++++---
>  2 files changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/migrate.h b/include/linux/migrate.h
> index db96e10eb8da..66a34eae8cb6 100644
> --- a/include/linux/migrate.h
> +++ b/include/linux/migrate.h
> @@ -130,6 +130,7 @@ static inline unsigned long migrate_pfn(unsigned long pfn)
>  enum migrate_vma_direction {
>  	MIGRATE_VMA_SELECT_SYSTEM = 1 << 0,
>  	MIGRATE_VMA_SELECT_DEVICE_PRIVATE = 1 << 1,
> +	MIGRATE_VMA_SELECT_DEVICE_COHERENT = 1 << 2,
>  };
>  
>  struct migrate_vma {
> diff --git a/mm/migrate.c b/mm/migrate.c
> index cd137aedcfe5..69c6830c47c6 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -2264,15 +2264,21 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
>  			if (is_writable_device_private_entry(entry))
>  				mpfn |= MIGRATE_PFN_WRITE;
>  		} else {
> -			if (!(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM))
> -				goto next;
>  			pfn = pte_pfn(pte);
> -			if (is_zero_pfn(pfn)) {
> +			if (is_zero_pfn(pfn) &&
> +			    (migrate->flags & MIGRATE_VMA_SELECT_SYSTEM)) {
>  				mpfn = MIGRATE_PFN_MIGRATE;
>  				migrate->cpages++;
>  				goto next;
>  			}
>  			page = vm_normal_page(migrate->vma, addr, pte);
> +			if (page && !is_zone_device_page(page) &&
> +			    !(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM))
> +				goto next;
> +			else if (page && is_device_coherent_page(page) &&
> +			    (!(migrate->flags & MIGRATE_VMA_SELECT_DEVICE_COHERENT) ||
> +			     page->pgmap->owner != migrate->pgmap_owner))
> +				goto next;
>  			mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
>  			mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
>  		}
>