KVM: nVMX: Don't emulate instructions in guest mode

vmx_check_intercept is not yet fully implemented. To avoid emulating
instructions disallowed by the L1 hypervisor, refuse to emulate
instructions by default.

Cc: [email protected]
[Made commit, added commit msg - Oliver]
Signed-off-by: Oliver Upton <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>

(cherry picked from commit 07721fe)

Orabug: 30847133
CVE: CVE-2020-2732

Signed-off-by: Boris Ostrovsky <[email protected]>
Reviewed-by: Darren Kenny <[email protected]>

Author: bonzini

arch/x86/kvm/vmx/vmx.c

@@ -7196,7 +7196,7 @@ static int vmx_check_intercept(struct kvm_vcpu *vcpu,
 	}
 
 	/* TODO: check more intercepts... */
-	return X86EMUL_CONTINUE;
+	return X86EMUL_UNHANDLEABLE;
 }
 
 #ifdef CONFIG_X86_64