[PATCH] KVM: x86: Fix device passthrough when SME is active

[Tom Lendacky <thomas.lendacky@amd.com>]

When using device passthrough with SME active, the MMIO range that is
mapped for the device should not be mapped encrypted.  Add a check in
set_spte() to insure that a page is not mapped encrypted if that page
is a device MMIO page as indicated by kvm_is_mmio_pfn().

Cc: <stable@vger.kernel.org> # 4.14.x-
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 arch/x86/kvm/mmu.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index f551962..763bb3b 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2770,8 +2770,10 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
 	else
 		pte_access &= ~ACC_WRITE_MASK;
 
+	if (!kvm_is_mmio_pfn(pfn))
+		spte |= shadow_me_mask;
+
 	spte |= (u64)pfn << PAGE_SHIFT;
-	spte |= shadow_me_mask;
 
 	if (pte_access & ACC_WRITE_MASK) {