[Xen-devel] [PATCH RFC v1 10/12] powerpc/mm: Prepare maybe_pte_to_page() for PG_reserved changes

[David Hildenbrand <david@xxxxxxxxxx>]

Right now, ZONE_DEVICE memory is always set PG_reserved. We want to
change that.

We could explicitly check for is_zone_device_page(page). But looking at
the pfn_valid() check, it seems safer to just use pfn_to_online_page()
here, that will skip all ZONE_DEVICE pages right away.

Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Christophe Leroy <christophe.leroy@xxxxxx>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxx>
Cc: Allison Randal <allison@xxxxxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
---
 arch/powerpc/mm/pgtable.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
index e3759b69f81b..613c98fa7dc0 100644
--- a/arch/powerpc/mm/pgtable.c
+++ b/arch/powerpc/mm/pgtable.c
@@ -55,10 +55,12 @@ static struct page *maybe_pte_to_page(pte_t pte)
        unsigned long pfn = pte_pfn(pte);
        struct page *page;
 
-       if (unlikely(!pfn_valid(pfn)))
-               return NULL;
-       page = pfn_to_page(pfn);
-       if (PageReserved(page))
+       /*
+        * We reject any pages that are not online (not managed by the buddy).
+        * This includes ZONE_DEVICE pages.
+        */
+       page = pfn_to_online_page(pfn);
+       if (unlikely(!page || PageReserved(page)))
                return NULL;
        return page;
 }
-- 
2.21.0


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