KVM: SVM: Don't allow nested guest to VMMCALL into host

This patch disables the possibility for a l2-guest to do a
VMMCALL directly into the host. This would happen if the
l1-hypervisor doesn't intercept VMMCALL and the l2-guest
executes this instruction.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 2511664..4a66ffe 100644 (file)
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -2036,6 +2036,9 @@ static bool nested_svm_vmrun(struct vcpu_svm *svm)
                svm->vmcb->control.intercept_cr_write &= ~INTERCEPT_CR8_MASK;
        }
 
+       /* We don't want to see VMMCALLs from a nested guest */
+       svm->vmcb->control.intercept &= ~(1ULL << INTERCEPT_VMMCALL);
+
        /*
         * We don't want a nested guest to be more powerful than the guest, so
         * all intercepts are ORed