[PATCH v7 10/13] s390x: kvm: topology: interception of PTF instruction

[Pierre Morel <pmorel@xxxxxxxxxxxxx>]

When the host supports the CPU topology facility, the PTF
instruction with function code 2 is interpreted by the SIE,
provided that the userland hypervizor activates the interpretation
by using the KVM_CAP_S390_CPU_TOPOLOGY KVM extension.

The PTF instructions with function code 0 and 1 are intercepted
and must be emulated by the userland hypervizor.

Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
---
 hw/s390x/s390-virtio-ccw.c         | 50 ++++++++++++++++++++++++++++++
 include/hw/s390x/s390-virtio-ccw.h |  6 ++++
 target/s390x/kvm/kvm.c             | 14 +++++++++
 3 files changed, 70 insertions(+)

diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index 93d1a43583..1ffaddebcc 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -434,6 +434,56 @@ static void s390_pv_prepare_reset(S390CcwMachineState *ms)
     s390_pv_prep_reset();
 }
 
+/*
+ * s390_handle_ptf:
+ *
+ * @register 1: contains the function code
+ *
+ * Function codes 0 and 1 handle the CPU polarization.
+ * We assume an horizontal topology, the only one supported currently
+ * by Linux, consequently we answer to function code 0, requesting
+ * horizontal polarization that it is already the current polarization
+ * and reject vertical polarization request without further explanation.
+ *
+ * Function code 2 is handling topology changes and is interpreted
+ * by the SIE.
+ */
+int s390_handle_ptf(S390CPU *cpu, uint8_t r1, uintptr_t ra)
+{
+    CPUS390XState *env = &cpu->env;
+    uint64_t reg = env->regs[r1];
+    uint8_t fc = reg & S390_TOPO_FC_MASK;
+
+    if (!s390_has_feat(S390_FEAT_CONFIGURATION_TOPOLOGY)) {
+        s390_program_interrupt(env, PGM_OPERATION, ra);
+        return 0;
+    }
+
+    if (env->psw.mask & PSW_MASK_PSTATE) {
+        s390_program_interrupt(env, PGM_PRIVILEGED, ra);
+        return 0;
+    }
+
+    if (reg & ~S390_TOPO_FC_MASK) {
+        s390_program_interrupt(env, PGM_SPECIFICATION, ra);
+        return 0;
+    }
+
+    switch (fc) {
+    case 0:    /* Horizontal polarization is already set */
+        env->regs[r1] |= S390_PTF_REASON_DONE;
+        return 2;
+    case 1:    /* Vertical polarization is not supported */
+        env->regs[r1] |= S390_PTF_REASON_NONE;
+        return 2;
+    default:
+        /* Note that fc == 2 is interpreted by the SIE */
+        s390_program_interrupt(env, PGM_SPECIFICATION, ra);
+    }
+
+    return 0;
+}
+
 static void s390_machine_reset(MachineState *machine)
 {
     S390CcwMachineState *ms = S390_CCW_MACHINE(machine);
diff --git a/include/hw/s390x/s390-virtio-ccw.h b/include/hw/s390x/s390-virtio-ccw.h
index 3331990e02..ac4b4a92e7 100644
--- a/include/hw/s390x/s390-virtio-ccw.h
+++ b/include/hw/s390x/s390-virtio-ccw.h
@@ -30,6 +30,12 @@ struct S390CcwMachineState {
     uint8_t loadparm[8];
 };
 
+#define S390_PTF_REASON_NONE (0x00 << 8)
+#define S390_PTF_REASON_DONE (0x01 << 8)
+#define S390_PTF_REASON_BUSY (0x02 << 8)
+#define S390_TOPO_FC_MASK 0xffUL
+int s390_handle_ptf(S390CPU *cpu, uint8_t r1, uintptr_t ra);
+
 struct S390CcwMachineClass {
     /*< private >*/
     MachineClass parent_class;
diff --git a/target/s390x/kvm/kvm.c b/target/s390x/kvm/kvm.c
index 27b3fbfa09..e3792e52c2 100644
--- a/target/s390x/kvm/kvm.c
+++ b/target/s390x/kvm/kvm.c
@@ -98,6 +98,7 @@
 
 #define PRIV_B9_EQBS                    0x9c
 #define PRIV_B9_CLP                     0xa0
+#define PRIV_B9_PTF                     0xa2
 #define PRIV_B9_PCISTG                  0xd0
 #define PRIV_B9_PCILG                   0xd2
 #define PRIV_B9_RPCIT                   0xd3
@@ -1453,6 +1454,16 @@ static int kvm_mpcifc_service_call(S390CPU *cpu, struct kvm_run *run)
     }
 }
 
+static int kvm_handle_ptf(S390CPU *cpu, struct kvm_run *run)
+{
+    uint8_t r1 = (run->s390_sieic.ipb >> 20) & 0x0f;
+    int ret;
+
+    ret = s390_handle_ptf(cpu, r1, RA_IGNORED);
+    setcc(cpu, ret);
+    return 0;
+}
+
 static int handle_b9(S390CPU *cpu, struct kvm_run *run, uint8_t ipa1)
 {
     int r = 0;
@@ -1470,6 +1481,9 @@ static int handle_b9(S390CPU *cpu, struct kvm_run *run, uint8_t ipa1)
     case PRIV_B9_RPCIT:
         r = kvm_rpcit_service_call(cpu, run);
         break;
+    case PRIV_B9_PTF:
+        r = kvm_handle_ptf(cpu, run);
+        break;
     case PRIV_B9_EQBS:
         /* just inject exception */
         r = -1;
-- 
2.27.0