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From:   Alex Sierra <alex.sierra@amd.com>
To:     <akpm@linux-foundation.org>, <Felix.Kuehling@amd.com>,
        <linux-mm@kvack.org>, <rcampbell@nvidia.com>,
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Subject: [PATCH v5 02/10] mm: add device coherent vma selection for memory migration
Date:   Fri, 28 Jan 2022 14:08:17 -0600
Message-ID: <20220128200825.8623-3-alex.sierra@amd.com>
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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@amd.com>
Acked-by: Felix Kuehling <Felix.Kuehling@amd.com>
---
v2:
condition added when migrations from device coherent pages.
---
 include/linux/migrate.h |  1 +
 mm/migrate.c            | 10 +++++++++-
 2 files changed, 10 insertions(+), 1 deletion(-)

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..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)) {
@@ -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;
 		}
-- 
2.32.0