On Tue, Aug 27, 2024 at 07:48:37PM -0700, Matthew Brost wrote:
> Add migrate_device_vma_range which prepares an array of pre-populated
> device pages for migration and issues a MMU invalidation.
>
> Cc: Andrew Morton <a...@linux-foundation.org>
> Signed-off-by: Matthew Brost <matthew.br...@intel.com>
> ---
> include/linux/migrate.h | 3 +++
> mm/migrate_device.c | 53 +++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 56 insertions(+)
>
> diff --git a/include/linux/migrate.h b/include/linux/migrate.h
> index 644be30b69c8..e8cce05bf9c2 100644
> --- a/include/linux/migrate.h
> +++ b/include/linux/migrate.h
> @@ -226,6 +226,9 @@ void migrate_vma_pages(struct migrate_vma *migrate);
> void migrate_vma_finalize(struct migrate_vma *migrate);
> int migrate_device_range(unsigned long *src_pfns, unsigned long start,
> unsigned long npages);
> +int migrate_device_vma_range(struct mm_struct *mm, void *pgmap_owner,
> + unsigned long *src_pfns, unsigned long npages,
> + unsigned long start);
> void migrate_device_pages(unsigned long *src_pfns, unsigned long *dst_pfns,
> unsigned long npages);
> void migrate_device_finalize(unsigned long *src_pfns,
> diff --git a/mm/migrate_device.c b/mm/migrate_device.c
> index 6d66dc1c6ffa..e25f12a132e8 100644
> --- a/mm/migrate_device.c
> +++ b/mm/migrate_device.c
> @@ -920,6 +920,59 @@ int migrate_device_range(unsigned long *src_pfns,
> unsigned long start,
> }
> EXPORT_SYMBOL(migrate_device_range);
>
> +/**
> + * migrate_device_vma_range() - migrate device private pfns to normal memory
> and
> + * trigger MMU invalidation.
> + * @mm: struct mm of device pages.
> + * @src_pfns: pre-popluated array of source device private pfns to migrate.
> + * @pgmap_owner: page group map owner of device pages.
> + * @npages: number of pages to migrate.
> + * @start: VMA start of device pages.
> + *
> + * Similar to migrate_device_range() but supports non-contiguous
> pre-popluated
> + * array of device pages to migrate. Also triggers MMU invalidation. Useful
> in
> + * device memory eviction paths where lock is held protecting the device
> pages
> + * but where the mmap lock cannot be taken to due to a locking inversion
> (e.g.
> + * DRM drivers). Since the mmap lock is not required to be held, the MMU
> + * invalidation can race with with VMA start being repurposed, worst case
> this
> + * would result in an unecessary invalidation.
> + */
> +int migrate_device_vma_range(struct mm_struct *mm, void *pgmap_owner,
> + unsigned long *src_pfns, unsigned long npages,
> + unsigned long start)
> +{
> + struct mmu_notifier_range range;
> + unsigned long i;
> +
> + mmu_notifier_range_init_owner(&range, MMU_NOTIFY_MIGRATE, 0,
> + mm, start, start + npages * PAGE_SIZE,
> + pgmap_owner);
> + mmu_notifier_invalidate_range_start(&range);
This isn't needed, try_to_migrate called from migrate_device_unmap already
has a notifier, if there's actually any ptes to clear. If you need this
one you've missed a pte clear notification somewhere, or there's some
other bad bug somewhere.
-Sima
> +
> + for (i = 0; i < npages; i++) {
> + struct page *page = pfn_to_page(src_pfns[i]);
> +
> + if (!get_page_unless_zero(page)) {
> + src_pfns[i] = 0;
> + continue;
> + }
> +
> + if (!trylock_page(page)) {
> + src_pfns[i] = 0;
> + put_page(page);
> + continue;
> + }
> +
> + src_pfns[i] = migrate_pfn(src_pfns[i]) | MIGRATE_PFN_MIGRATE;
> + }
> +
> + migrate_device_unmap(src_pfns, npages, NULL);
> + mmu_notifier_invalidate_range_end(&range);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(migrate_device_vma_range);
> +
> /*
> * Migrate a device coherent page back to normal memory. The caller should
> have
> * a reference on page which will be copied to the new page if migration is
> --
> 2.34.1
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
