[qemu-s390x] [PATCH v3 6/7] s390x/kvm: handle AP instruction interception

[Tony Krowiak]

If the CPU model indicates that AP facility is installed on
the guest (i.e., -cpu xxxx,ap=on), then the expectation is that
the AP bus running in the guest will initialize; however, if the
AP instructions are not being interpreted by the firmware, then
they will be intercepted and routed back to QEMU for handling.
If a handler is not defined to process the intercepted instruciton,
then an operation exception will be injected into the
guest, in which case the AP bus will not initialize.

There are two situations where AP instructions will not be
interpreted:

1. The guest is not configured with a vfio-ap device (i.e.,
   -device vfio-ap,sysfsdev=$path-to-mdev). The realize function for
   the vfio-ap device enables interpretive execution of AP
   instructions.

2. The guest is a second level guest but the first level guest has
   not enabled interpretive execution.

This patch introduces AP instruction handlers to ensure the AP bus
module initializes on the guest when the AP facility is installed
on the guest but AP instructions are not being interpreted. The logic
incorporated is:

* If the CPU model indicates AP instructions are
  installed

  * Set the status response code for the instruction to indicate that
    the APQN contained in the instruction is not valid. This is
    a valid response because there will be no devices configured for
    the guest in any of the above scenarios.

* Else return an error from the handler. This will result in an
  operation being injected into the guest and the AP bus will not
  initialize on the guest. That is commensurate with how things work
  today.

Signed-off-by: Tony Krowiak <address@hidden>
---
 hw/vfio/ap.c                 |   45 ++++++++++++++++++++++++++++++++++++++++++
 include/hw/s390x/ap-device.h |    6 +++++
 target/s390x/kvm.c           |   14 +++++++++++++
 3 files changed, 65 insertions(+), 0 deletions(-)

diff --git a/hw/vfio/ap.c b/hw/vfio/ap.c
index b397bb1..88e744d 100644
--- a/hw/vfio/ap.c
+++ b/hw/vfio/ap.c
@@ -148,6 +148,51 @@ static void vfio_ap_unrealize(DeviceState *dev, Error 
**errp)
     kvm_s390_set_interpret_ap(0);
 }
 
+int ap_device_handle_nqap(S390CPU *cpu)
+{
+    CPUS390XState *env = &cpu->env;
+
+    if (s390_has_feat(S390_FEAT_AP)) {
+        env->regs[1] = 0x10000;
+
+        return 0;
+    }
+
+    return -EOPNOTSUPP;
+}
+
+int ap_device_handle_dqap(S390CPU *cpu)
+{
+    CPUS390XState *env = &cpu->env;
+
+    if (s390_has_feat(S390_FEAT_AP)) {
+        env->regs[1] = 0x10000;
+
+        return 0;
+    }
+
+    return -EOPNOTSUPP;
+}
+
+int ap_device_handle_pqap(S390CPU *cpu)
+{
+    CPUS390XState *env = &cpu->env;
+    int fc = 4 & (env->regs[0] >> 24);
+
+    /*
+     * The Query Configuration Information (QCI) function (fc == 4) does not
+     * set a response code in reg 1, so check for that along with the
+     * AP feature.
+     */
+    if ((fc != 4) && s390_has_feat(S390_FEAT_AP)) {
+        env->regs[1] = 0x10000;
+
+        return 0;
+    }
+
+    return -EOPNOTSUPP;
+}
+
 static Property vfio_ap_properties[] = {
     DEFINE_PROP_STRING("sysfsdev", VFIOAPDevice, vdev.sysfsdev),
     DEFINE_PROP_END_OF_LIST(),
diff --git a/include/hw/s390x/ap-device.h b/include/hw/s390x/ap-device.h
index 693df90..d45ae38 100644
--- a/include/hw/s390x/ap-device.h
+++ b/include/hw/s390x/ap-device.h
@@ -11,6 +11,8 @@
 #ifndef HW_S390X_AP_DEVICE_H
 #define HW_S390X_AP_DEVICE_H
 
+#include "cpu.h"
+
 #define AP_DEVICE_TYPE       "ap-device"
 
 typedef struct APDevice {
@@ -35,4 +37,8 @@ static inline APDevice *to_ap_dev(DeviceState *dev)
 #define AP_DEVICE_CLASS(klass) \
     OBJECT_CLASS_CHECK(APDeviceClass, (klass), AP_DEVICE_TYPE)
 
+int ap_device_handle_nqap(S390CPU *cpu);
+int ap_device_handle_dqap(S390CPU *cpu);
+int ap_device_handle_pqap(S390CPU *cpu);
+
 #endif /* HW_S390X_AP_DEVICE_H */
diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
index 2812e28..a636394 100644
--- a/target/s390x/kvm.c
+++ b/target/s390x/kvm.c
@@ -50,6 +50,7 @@
 #include "exec/memattrs.h"
 #include "hw/s390x/s390-virtio-ccw.h"
 #include "hw/s390x/s390-virtio-hcall.h"
+#include "hw/s390x/ap-device.h"
 
 #ifndef DEBUG_KVM
 #define DEBUG_KVM  0
@@ -88,6 +89,9 @@
 #define PRIV_B2_CHSC                    0x5f
 #define PRIV_B2_SIGA                    0x74
 #define PRIV_B2_XSCH                    0x76
+#define PRIV_B2_NQAP                    0xad
+#define PRIV_B2_DQAP                    0xae
+#define PRIV_B2_PQAP                    0xaf
 
 #define PRIV_EB_SQBS                    0x8a
 #define PRIV_EB_PCISTB                  0xd0
@@ -1245,6 +1249,16 @@ static int handle_b2(S390CPU *cpu, struct kvm_run *run, 
uint8_t ipa1)
     case PRIV_B2_SCLP_CALL:
         rc = kvm_sclp_service_call(cpu, run, ipbh0);
         break;
+    case PRIV_B2_NQAP:
+        rc = ap_device_handle_nqap(cpu);
+        break;
+    case PRIV_B2_DQAP:
+        rc = ap_device_handle_dqap(cpu);
+        break;
+    case PRIV_B2_PQAP:
+        rc = ap_device_handle_pqap(cpu);
+        break;
+        break;
     default:
         rc = -1;
         DPRINTF("KVM: unhandled PRIV: 0xb2%x\n", ipa1);
-- 
1.7.1