s390x/kvm: Guest Migration TOD clock synchronization

Synchronizes the guest TOD clock across a migration by sending the guest TOD
clock value to the destination system. If the guest TOD clock is not preserved
across a migration then the guest's view of time will snap backwards if the
destination host clock is behind the source host clock. This will cause the
guest to hang immediately upon resuming on the destination system.

Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Jason J. Herne <jjherne@linux.vnet.ibm.com>
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>

Message-Id: <1425912968-54387-1-git-send-email-jfrei@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>

2 files changed, 73 insertions, 0 deletions

diff --git a/target-s390x/cpu.h b/target-s390x/cpu.h
index 0171de0179..8135dda318 100644
--- a/target-s390x/cpu.h
+++ b/target-s390x/cpu.h
@@ -401,6 +401,8 @@ void kvm_s390_vcpu_interrupt(S390CPU *cpu, struct kvm_s390_irq *irq);
 void kvm_s390_floating_interrupt(struct kvm_s390_irq *irq);
 int kvm_s390_inject_flic(struct kvm_s390_irq *irq);
 void kvm_s390_access_exception(S390CPU *cpu, uint16_t code, uint64_t te_code);
+int kvm_s390_get_clock(uint8_t *tod_high, uint64_t *tod_clock);
+int kvm_s390_set_clock(uint8_t *tod_high, uint64_t *tod_clock);
 #else
 static inline void kvm_s390_virtio_irq(int config_change, uint64_t token)
 {
@@ -408,11 +410,40 @@ static inline void kvm_s390_virtio_irq(int config_change, uint64_t token)
 static inline void kvm_s390_service_interrupt(uint32_t parm)
 {
 }
+static inline int kvm_s390_get_clock(uint8_t *tod_high, uint64_t *tod_low)
+{
+    return -ENOSYS;
+}
+static inline int kvm_s390_set_clock(uint8_t *tod_high, uint64_t *tod_low)
+{
+    return -ENOSYS;
+}
 static inline void kvm_s390_access_exception(S390CPU *cpu, uint16_t code,
                                              uint64_t te_code)
 {
 }
 #endif
+
+static inline int s390_get_clock(uint8_t *tod_high, uint64_t *tod_low)
+{
+    if (kvm_enabled()) {
+        return kvm_s390_get_clock(tod_high, tod_low);
+    }
+    /* Fixme TCG */
+    *tod_high = 0;
+    *tod_low = 0;
+    return 0;
+}
+
+static inline int s390_set_clock(uint8_t *tod_high, uint64_t *tod_low)
+{
+    if (kvm_enabled()) {
+        return kvm_s390_set_clock(tod_high, tod_low);
+    }
+    /* Fixme TCG */
+    return 0;
+}
+
 S390CPU *s390_cpu_addr2state(uint16_t cpu_addr);
 unsigned int s390_cpu_halt(S390CPU *cpu);
 void s390_cpu_unhalt(S390CPU *cpu);
@@ -422,6 +453,9 @@ static inline uint8_t s390_cpu_get_state(S390CPU *cpu)
     return cpu->env.cpu_state;
 }
 
+void gtod_save(QEMUFile *f, void *opaque);
+int gtod_load(QEMUFile *f, void *opaque, int version_id);
+
 /* service interrupts are floating therefore we must not pass an cpustate */
 void s390_sclp_extint(uint32_t parm);
 
diff --git a/target-s390x/kvm.c b/target-s390x/kvm.c
index 896534bf95..b21a348805 100644
--- a/target-s390x/kvm.c
+++ b/target-s390x/kvm.c
@@ -486,6 +486,45 @@ int kvm_arch_get_registers(CPUState *cs)
     return 0;
 }
 
+int kvm_s390_get_clock(uint8_t *tod_high, uint64_t *tod_low)
+{
+    int r;
+    struct kvm_device_attr attr = {
+        .group = KVM_S390_VM_TOD,
+        .attr = KVM_S390_VM_TOD_LOW,
+        .addr = (uint64_t)tod_low,
+    };
+
+    r = kvm_vm_ioctl(kvm_state, KVM_GET_DEVICE_ATTR, &attr);
+    if (r) {
+        return r;
+    }
+
+    attr.attr = KVM_S390_VM_TOD_HIGH;
+    attr.addr = (uint64_t)tod_high;
+    return kvm_vm_ioctl(kvm_state, KVM_GET_DEVICE_ATTR, &attr);
+}
+
+int kvm_s390_set_clock(uint8_t *tod_high, uint64_t *tod_low)
+{
+    int r;
+
+    struct kvm_device_attr attr = {
+        .group = KVM_S390_VM_TOD,
+        .attr = KVM_S390_VM_TOD_LOW,
+        .addr = (uint64_t)tod_low,
+    };
+
+    r = kvm_vm_ioctl(kvm_state, KVM_SET_DEVICE_ATTR, &attr);
+    if (r) {
+        return r;
+    }
+
+    attr.attr = KVM_S390_VM_TOD_HIGH;
+    attr.addr = (uint64_t)tod_high;
+    return kvm_vm_ioctl(kvm_state, KVM_SET_DEVICE_ATTR, &attr);
+}
+
 /*
  * Legacy layout for s390:
  * Older S390 KVM requires the topmost vma of the RAM to be