[PATCH 4.19 255/361] KVM: arm/arm64: Ensure only THP is candidate for adjustment

Greg Kroah-Hartman
2018-11-11T23:56:23Z

From: Punit Agrawal <punit.agrawal@arm.com>

commit fd2ef358282c849c193aa36dadbf4f07f7dcd29b upstream.

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@arm.com>
Reviewed-by: Suzuki Poulose <suzuki.poulose@arm.com>
Cc: Christoffer Dall <christoffer.dall@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: stable@vger.kernel.org # v4.13+
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
virt/kvm/arm/mmu.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -1230,8 +1230,14 @@ static bool transparent_hugepage_adjust(
{
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