linux-kernel - [PATCH v8 1/9] KVM: arm/arm64: Ensure only THP is candidate for adjustment

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Date:   Mon,  1 Oct 2018 16:54:35 +0100
From:   Punit Agrawal <punit.agrawal@....com>
To:     kvmarm@...ts.cs.columbia.edu
Cc:     Punit Agrawal <punit.agrawal@....com>, marc.zyngier@....com,
        will.deacon@....com, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, suzuki.poulose@....com,
        Christoffer Dall <christoffer.dall@....com>,
        stable@...r.kernel.org
Subject: [PATCH v8 1/9] KVM: arm/arm64: Ensure only THP is candidate for adjustment

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@....com>
Reviewed-by: Suzuki Poulose <suzuki.poulose@....com>
Cc: Christoffer Dall <christoffer.dall@....com>
Cc: Marc Zyngier <marc.zyngier@....com>
Cc: stable@...r.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