1 files changed, 24 insertions, 8 deletions

diff --git a/arch/s390/kvm/intercept.c b/arch/s390/kvm/intercept.c
index 0ee02dae14b2..2cda8d9d7c6e 100644
--- a/arch/s390/kvm/intercept.c
+++ b/arch/s390/kvm/intercept.c
@@ -271,10 +271,18 @@ static int handle_prog(struct kvm_vcpu *vcpu)
  * handle_external_interrupt - used for external interruption interceptions
  * @vcpu: virtual cpu
  *
- * This interception only occurs if the CPUSTAT_EXT_INT bit was set, or if
- * the new PSW does not have external interrupts disabled. In the first case,
- * we've got to deliver the interrupt manually, and in the second case, we
- * drop to userspace to handle the situation there.
+ * This interception occurs if:
+ * - the CPUSTAT_EXT_INT bit was already set when the external interrupt
+ *   occurred. In this case, the interrupt needs to be injected manually to
+ *   preserve interrupt priority.
+ * - the external new PSW has external interrupts enabled, which will cause an
+ *   interruption loop. We drop to userspace in this case.
+ *
+ * The latter case can be detected by inspecting the external mask bit in the
+ * external new psw.
+ *
+ * Under PV, only the latter case can occur, since interrupt priorities are
+ * handled in the ultravisor.
  */
 static int handle_external_interrupt(struct kvm_vcpu *vcpu)
 {
@@ -285,10 +293,18 @@ static int handle_external_interrupt(struct kvm_vcpu *vcpu)
 
 	vcpu->stat.exit_external_interrupt++;
 
-	rc = read_guest_lc(vcpu, __LC_EXT_NEW_PSW, &newpsw, sizeof(psw_t));
-	if (rc)
-		return rc;
-	/* We can not handle clock comparator or timer interrupt with bad PSW */
+	if (kvm_s390_pv_cpu_is_protected(vcpu)) {
+		newpsw = vcpu->arch.sie_block->gpsw;
+	} else {
+		rc = read_guest_lc(vcpu, __LC_EXT_NEW_PSW, &newpsw, sizeof(psw_t));
+		if (rc)
+			return rc;
+	}
+
+	/*
+	 * Clock comparator or timer interrupt with external interrupt enabled
+	 * will cause interrupt loop. Drop to userspace.
+	 */
 	if ((eic == EXT_IRQ_CLK_COMP || eic == EXT_IRQ_CPU_TIMER) &&
 	    (newpsw.mask & PSW_MASK_EXT))
 		return -EOPNOTSUPP;