On Saturday, 29 January 2022 7:08:17 AM AEDT Alex Sierra wrote:
[...]
struct migrate_vma { diff --git a/mm/migrate.c b/mm/migrate.c index cd137aedcfe5..d3cc3589e1e8 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -2264,7 +2264,8 @@ 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))
if (!(migrate->flags & MIGRATE_VMA_SELECT_SYSTEM) &&!(migrate->flags & MIGRATE_VMA_SELECT_DEVICE_COHERENT)) goto next; pfn = pte_pfn(pte); if (is_zero_pfn(pfn)) {
Sorry, but I still don't think this is quite right.
When specifying MIGRATE_VMA_SELECT_DEVICE_COHERENT we are looking for pages to migrate from the device back to system memory. But as currently written I think this can also select the zero pfn when MIGRATE_VMA_SELECT_DEVICE_COHERENT is specified. As far as I know that can never point to device memory so migration of a zero pfn should be also be skipped in that case.
We should only migrate the zero pfn if MIGRATE_VMA_SELECT_SYSTEM is specified.
@@ -2273,6 +2274,13 @@ 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;