linux-ext4 - [PATCH v8 05/15] mm: add device coherent vma selection for memory migration

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Date:   Thu, 7 Jul 2022 14:03:39 -0500
From:   Alex Sierra <alex.sierra@....com>
To:     <jgg@...dia.com>
CC:     <david@...hat.com>, <Felix.Kuehling@....com>, <linux-mm@...ck.org>,
        <rcampbell@...dia.com>, <linux-ext4@...r.kernel.org>,
        <linux-xfs@...r.kernel.org>, <amd-gfx@...ts.freedesktop.org>,
        <dri-devel@...ts.freedesktop.org>, <hch@....de>,
        <jglisse@...hat.com>, <apopple@...dia.com>, <willy@...radead.org>,
        <akpm@...ux-foundation.org>
Subject: [PATCH v8 05/15] mm: add device coherent vma selection for memory migration

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@....com>
Acked-by: Felix Kuehling <Felix.Kuehling@....com>
Reviewed-by: Alistair Poppple <apopple@...dia.com>
Signed-off-by: Christoph Hellwig <hch@....de>
Reviewed-by: David Hildenbrand <david@...hat.com>
---
 include/linux/migrate.h |  1 +
 mm/migrate_device.c     | 12 +++++++++---
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index 069a89e847f3..b84908debe5c 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -148,6 +148,7 @@ 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_device.c b/mm/migrate_device.c
index a4847ad65da3..18bc6483f63a 100644
--- a/mm/migrate_device.c
+++ b/mm/migrate_device.c
@@ -148,15 +148,21 @@ 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;
 		}
-- 
2.32.0