[PATCH 4.12 36/99] KVM: x86: block guest protection keys unless the host has them enabled

[Greg Kroah-Hartman]

4.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Paolo Bonzini <pbonzini@xxxxxxxxxx>

commit c469268cd523245cc58255f6696e0c295485cb0b upstream.

If the host has protection keys disabled, we cannot read and write the
guest PKRU---RDPKRU and WRPKRU fail with #GP(0) if CR4.PKE=0.  Block
the PKU cpuid bit in that case.

This ensures that guest_CR4.PKE=1 implies host_CR4.PKE=1.

Fixes: 1be0e61c1f255faaeab04a390e00c8b9b9042870
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/x86/kvm/cpuid.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -469,7 +469,7 @@ static inline int __do_cpuid_ent(struct
 			entry->ecx &= kvm_cpuid_7_0_ecx_x86_features;
 			cpuid_mask(&entry->ecx, CPUID_7_ECX);
 			/* PKU is not yet implemented for shadow paging. */
-			if (!tdp_enabled)
+			if (!tdp_enabled || !boot_cpu_has(X86_FEATURE_OSPKE))
 				entry->ecx &= ~F(PKU);
 			entry->edx &= kvm_cpuid_7_0_edx_x86_features;
 			entry->edx &= get_scattered_cpuid_leaf(7, 0, CPUID_EDX);