Re: [PATCH v4 02/10] mm: add device coherent vma selection for memory migration

On Thursday, 27 January 2022 2:09:41 PM AEDT Alex Sierra wrote:

[...]

diff --git a/mm/migrate.c b/mm/migrate.c index 277562cd4cf5..2b3375e165b1 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -2340,8 +2340,6 @@ 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;
  

This isn't correct as it allows zero pfn pages to be selected for migration when they shouldn't be (ie. because MIGRATE_VMA_SELECT_SYSTEM isn't specified).

	pfn = pte_pfn(pte);
	if (is_zero_pfn(pfn)) {
		mpfn = MIGRATE_PFN_MIGRATE;

@@ -2349,6 +2347,13 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, 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;
  

• 	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;
  

  }