KVM: s390: Fix external interrupt interception

The external interrupt interception can only occur in rare cases, e.g.
when the PSW of the interrupt handler has a bad value. The old handler
for this interception simply ignored these events (except for increasing
the exit_external_interrupt counter), but for proper operation we either
have to inject the interrupts manually or we should drop to userspace in
case of errors.

Signed-off-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

2 files changed, 49 insertions, 5 deletions

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index f0a1dc5e5d1f..96b8a67ddaf8 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -132,7 +132,10 @@ struct kvm_s390_sie_block {
         psw_t   gpsw;                   /* 0x0090 */
         __u64   gg14;                   /* 0x00a0 */
         __u64   gg15;                   /* 0x00a8 */
-        __u8    reservedb0[28];         /* 0x00b0 */
+        __u8    reservedb0[20];         /* 0x00b0 */
+        __u16   extcpuaddr;             /* 0x00c4 */
+        __u16   eic;                    /* 0x00c6 */
+        __u32   reservedc8;             /* 0x00c8 */
         __u16   pgmilc;                 /* 0x00cc */
         __u16   iprcc;                  /* 0x00ce */
         __u32   dxc;                    /* 0x00d0 */
diff --git a/arch/s390/kvm/intercept.c b/arch/s390/kvm/intercept.c
index 99e4b76e3487..bd607cf01a5d 100644
--- a/arch/s390/kvm/intercept.c
+++ b/arch/s390/kvm/intercept.c
@@ -17,6 +17,7 @@
 
 #include <asm/kvm_host.h>
 #include <asm/asm-offsets.h>
+#include <asm/irq.h>
 
 #include "kvm-s390.h"
 #include "gaccess.h"
@@ -46,9 +47,6 @@ static int handle_noop(struct kvm_vcpu *vcpu)
         case 0x10:
                 vcpu->stat.exit_external_request++;
                 break;
-        case 0x14:
-                vcpu->stat.exit_external_interrupt++;
-                break;
         default:
                 break; /* nothing */
         }
@@ -234,6 +232,49 @@ static int handle_instruction_and_prog(struct kvm_vcpu *vcpu)
 }
 
 /**
+ * handle_external_interrupt - used for external interruption interceptions
+ *
+ * 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.
+ */
+static int handle_external_interrupt(struct kvm_vcpu *vcpu)
+{
+        u16 eic = vcpu->arch.sie_block->eic;
+        struct kvm_s390_interrupt irq;
+        psw_t newpsw;
+        int rc;
+
+        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 ((eic == EXT_IRQ_CLK_COMP || eic == EXT_IRQ_CPU_TIMER) &&
+            (newpsw.mask & PSW_MASK_EXT))
+                return -EOPNOTSUPP;
+
+        switch (eic) {
+        case EXT_IRQ_CLK_COMP:
+                irq.type = KVM_S390_INT_CLOCK_COMP;
+                break;
+        case EXT_IRQ_CPU_TIMER:
+                irq.type = KVM_S390_INT_CPU_TIMER;
+                break;
+        case EXT_IRQ_EXTERNAL_CALL:
+                irq.type = KVM_S390_INT_EXTERNAL_CALL;
+                irq.parm = vcpu->arch.sie_block->extcpuaddr;
+                break;
+        default:
+                return -EOPNOTSUPP;
+        }
+
+        return kvm_s390_inject_vcpu(vcpu, &irq);
+}
+
+/**
  * Handle MOVE PAGE partial execution interception.
  *
  * This interception can only happen for guests with DAT disabled and
@@ -291,7 +332,7 @@ static const intercept_handler_t intercept_funcs[] = {
         [0x08 >> 2] = handle_prog,
         [0x0C >> 2] = handle_instruction_and_prog,
         [0x10 >> 2] = handle_noop,
-        [0x14 >> 2] = handle_noop,
+        [0x14 >> 2] = handle_external_interrupt,
         [0x18 >> 2] = handle_noop,
         [0x1C >> 2] = kvm_s390_handle_wait,
         [0x20 >> 2] = handle_validity,