[PATCH v7 1/9] KVM: arm/arm64: Ensure only THP is candidate for adjustment

Punit Agrawal punit.agrawal at arm.com
Mon Sep 24 10:45:44 PDT 2018


PageTransCompoundMap() returns true for hugetlbfs and THP
hugepages. This behaviour incorrectly leads to stage 2 faults for
unsupported hugepage sizes (e.g., 64K hugepage with 4K pages) to be
treated as THP faults.

Tighten the check to filter out hugetlbfs pages. This also leads to
consistently mapping all unsupported hugepage sizes as PTE level
entries at stage 2.

Signed-off-by: Punit Agrawal <punit.agrawal at arm.com>
Cc: Christoffer Dall <christoffer.dall at arm.com>
Cc: Marc Zyngier <marc.zyngier at arm.com>
Cc: Suzuki Poulose <suzuki.poulose at arm.com>
Cc: stable at vger.kernel.org # v4.13+
---
 virt/kvm/arm/mmu.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index 7e477b3cae5b..c23a1b323aad 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -1231,8 +1231,14 @@ static bool transparent_hugepage_adjust(kvm_pfn_t *pfnp, phys_addr_t *ipap)
 {
 	kvm_pfn_t pfn = *pfnp;
 	gfn_t gfn = *ipap >> PAGE_SHIFT;
+	struct page *page = pfn_to_page(pfn);
 
-	if (PageTransCompoundMap(pfn_to_page(pfn))) {
+	/*
+	 * PageTransCompoungMap() returns true for THP and
+	 * hugetlbfs. Make sure the adjustment is done only for THP
+	 * pages.
+	 */
+	if (!PageHuge(page) && PageTransCompoundMap(page)) {
 		unsigned long mask;
 		/*
 		 * The address we faulted on is backed by a transparent huge
-- 
2.18.0




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