KVM: nSVM: restore clobbered INT_CTL fields after clearing VINTR

Restore the INT_CTL value from the guest's VMCB once we've stopped using
it, so that virtual interrupts can be injected as requested by L1.
V_TPR is up-to-date however, and it can change if the guest writes to CR8,
so keep it.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/svm/svm.c

@@ -1365,9 +1365,17 @@ static void svm_set_vintr(struct vcpu_svm *svm)
 
 static void svm_clear_vintr(struct vcpu_svm *svm)
 {
+	const u32 mask = V_TPR_MASK | V_GIF_ENABLE_MASK | V_GIF_MASK | V_INTR_MASKING_MASK;
 	clr_intercept(svm, INTERCEPT_VINTR);
 
-	svm->vmcb->control.int_ctl &= ~V_IRQ_MASK;
+	/* Drop int_ctl fields related to VINTR injection.  */
+	svm->vmcb->control.int_ctl &= mask;
+	if (is_guest_mode(&svm->vcpu)) {
+		WARN_ON((svm->vmcb->control.int_ctl & V_TPR_MASK) !=
+			(svm->nested.ctl.int_ctl & V_TPR_MASK));
+		svm->vmcb->control.int_ctl |= svm->nested.ctl.int_ctl & ~mask;
+	}
+
 	mark_dirty(svm->vmcb, VMCB_INTR);
 }