kvm: arm: Skip stage2 huge mappings for unaligned ipa backed by THP [Linux 5.1]

kvm: arm: Skip stage2 huge mappings for unaligned ipa backed by THP [Linux 5.1]

This Linux kernel change "kvm: arm: Skip stage2 huge mappings for unaligned ipa backed by THP" is included in the Linux 5.1 release. This change is authored by Suzuki K Poulose <suzuki.poulose [at] arm.com> on Wed Apr 10 16:14:57 2019 +0100. The commit for this change in Linux stable tree is 2e8010b (patch).

kvm: arm: Skip stage2 huge mappings for unaligned ipa backed by THP

With commit a80868f398554842b14, we no longer ensure that the
THP page is properly aligned in the guest IPA. Skip the stage2
huge mapping for unaligned IPA backed by transparent hugepages.

Fixes: a80868f398554842b14 ("KVM: arm/arm64: Enforce PTE mappings at stage2 when needed")
Reported-by: Eric Auger <[email protected]>
Cc: Marc Zyngier <[email protected]>
Cc: Chirstoffer Dall <[email protected]>
Cc: Zenghui Yu <[email protected]>
Cc: Zheng Xiang <[email protected]>
Cc: Andrew Murray <[email protected]>
Cc: Eric Auger <[email protected]>
Signed-off-by: Suzuki K Poulose <[email protected]>
Signed-off-by: Marc Zyngier <[email protected]>

There are 6 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 virt/kvm/arm/mmu.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index 27c9583..a39dcfd 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -1781,8 +1781,12 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
         * Only PMD_SIZE transparent hugepages(THP) are
         * currently supported. This code will need to be
         * updated to support other THP sizes.
+        *
+        * Make sure the host VA and the guest IPA are sufficiently
+        * aligned and that the block is contained within the memslot.
         */
-       if (transparent_hugepage_adjust(&pfn, &fault_ipa))
+       if (fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE) &&
+           transparent_hugepage_adjust(&pfn, &fault_ipa))
            vma_pagesize = PMD_SIZE;
    }

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