x86: kvm: mmu: use ept a/d in vmcs02 iff used in vmcs12

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EPT A/D was enabled in the vmcs02 EPTP regardless of the vmcs12's EPTP
value. The problem is that enabling A/D changes the behavior of L2's
x86 page table walks as seen by L1. With A/D enabled, x86 page table
walks are always treated as EPT writes.

Commit ae1e2d1082 ("kvm: nVMX: support EPT accessed/dirty bits",
2017-03-30) tried to work around this problem by clearing the write
bit in the exit qualification for EPT violations triggered by page
walks.  However, that fixup introduced the opposite bug: page-table walks
that actually set x86 A/D bits were *missing* the write bit in the exit
qualification.

This patch fixes the problem by disabling EPT A/D in the shadow MMU
when EPT A/D is disabled in vmcs12's EPTP.

Signed-off-by: Peter Feiner <pfeiner@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

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This commit is contained in:

Peter Feiner 2017-06-30 17:26:32 -07:00 • committed by Paolo Bonzini

parent ac8d57e573

commit 995f00a619

2 changed files with 18 additions and 21 deletions

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arch/x86/kvm/mmu.c

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38

arch/x86/kvm/vmx.c

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