[Qemu-devel] [PATCH v6 2/5] target-arm: kvm: save/restore mp state

["Alex Bennée" <alex.bennee@linaro.org>]

This adds the saving and restore of the current Multi-Processing state
of the machine. While the KVM_GET/SET_MP_STATE API exposes a number of
potential states for x86 we only use two for ARM. Either the process is
running or not. We then save this state into the cpu_powered TCG state
to avoid changing the serialisation format.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

---
v2
  - make mpstate field runtime dependant (kvm_enabled())
  - drop initial KVM_CAP_MP_STATE requirement
  - re-use cpu_powered instead of new field

v4
  - s/HALTED/STOPPED/
  - move code from machine.c to kvm.

v6
  - cache KVM_CAP_MP_STATE ioctl at start-up
  - reword commentary, add some apostrophes
  - invert errno for strerror

diff --git a/target-arm/kvm.c b/target-arm/kvm.c
index 72c1fa1..17371ca 100644
--- a/target-arm/kvm.c
+++ b/target-arm/kvm.c
@@ -28,6 +28,8 @@ const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
     KVM_CAP_LAST_INFO
 };
 
+static bool cap_has_mp_state = false;
+
 int kvm_arm_vcpu_init(CPUState *cs)
 {
     ARMCPU *cpu = ARM_CPU(cs);
@@ -157,6 +159,8 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
      */
     kvm_async_interrupts_allowed = true;
 
+    cap_has_mp_state = kvm_check_extension(s, KVM_CAP_MP_STATE);
+
     type_register_static(&host_arm_cpu_type_info);
 
     return 0;
@@ -458,6 +462,46 @@ void kvm_arm_reset_vcpu(ARMCPU *cpu)
     }
 }
 
+/*
+ * Update KVM's MP_STATE based on what QEMU thinks it is
+ */
+int kvm_arm_sync_mpstate_to_kvm(ARMCPU *cpu)
+{
+    if (cap_has_mp_state) {
+        struct kvm_mp_state mp_state = {
+            .mp_state =
+            cpu->powered_off ? KVM_MP_STATE_STOPPED : KVM_MP_STATE_RUNNABLE
+        };
+        int ret = kvm_vcpu_ioctl(CPU(cpu), KVM_SET_MP_STATE, &mp_state);
+        if (ret) {
+            fprintf(stderr, "%s: failed to set MP_STATE %d/%s\n",
+                    __func__, ret, strerror(-ret));
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
+/*
+ * Sync the KVM MP_STATE into QEMU
+ */
+int kvm_arm_sync_mpstate_to_qemu(ARMCPU *cpu)
+{
+    if (cap_has_mp_state) {
+        struct kvm_mp_state mp_state;
+        int ret = kvm_vcpu_ioctl(CPU(cpu), KVM_GET_MP_STATE, &mp_state);
+        if (ret) {
+            fprintf(stderr, "%s: failed to get MP_STATE %d/%s\n",
+                    __func__, ret, strerror(-ret));
+            abort();
+        }
+        cpu->powered_off = (mp_state.mp_state == KVM_MP_STATE_STOPPED);
+    }
+
+    return 0;
+}
+
 void kvm_arch_pre_run(CPUState *cs, struct kvm_run *run)
 {
 }
diff --git a/target-arm/kvm32.c b/target-arm/kvm32.c
index 94030d1..49b6bab 100644
--- a/target-arm/kvm32.c
+++ b/target-arm/kvm32.c
@@ -356,6 +356,8 @@ int kvm_arch_put_registers(CPUState *cs, int level)
         return EINVAL;
     }
 
+    kvm_arm_sync_mpstate_to_kvm(cpu);
+
     return ret;
 }
 
@@ -427,5 +429,7 @@ int kvm_arch_get_registers(CPUState *cs)
      */
     write_list_to_cpustate(cpu);
 
+    kvm_arm_sync_mpstate_to_qemu(cpu);
+
     return 0;
 }
diff --git a/target-arm/kvm64.c b/target-arm/kvm64.c
index 8cf3a62..fed03f2 100644
--- a/target-arm/kvm64.c
+++ b/target-arm/kvm64.c
@@ -211,6 +211,8 @@ int kvm_arch_put_registers(CPUState *cs, int level)
         return EINVAL;
     }
 
+    kvm_arm_sync_mpstate_to_kvm(cpu);
+
     /* TODO:
      * FP state
      */
@@ -310,6 +312,8 @@ int kvm_arch_get_registers(CPUState *cs)
      */
     write_list_to_cpustate(cpu);
 
+    kvm_arm_sync_mpstate_to_qemu(cpu);
+
     /* TODO: other registers */
     return ret;
 }
diff --git a/target-arm/kvm_arm.h b/target-arm/kvm_arm.h
index 455dea3..5abd591 100644
--- a/target-arm/kvm_arm.h
+++ b/target-arm/kvm_arm.h
@@ -162,6 +162,23 @@ typedef struct ARMHostCPUClass {
  */
 bool kvm_arm_get_host_cpu_features(ARMHostCPUClass *ahcc);
 
+
+/**
+ * kvm_arm_sync_mpstate_to_kvm
+ * @cpu: ARMCPU
+ *
+ * If supported set the KVM MP_STATE based on QEMU's model.
+ */
+int kvm_arm_sync_mpstate_to_kvm(ARMCPU *cpu);
+
+/**
+ * kvm_arm_sync_mpstate_to_qemu
+ * @cpu: ARMCPU
+ *
+ * If supported get the MP_STATE from KVM and store in QEMU's model.
+ */
+int kvm_arm_sync_mpstate_to_qemu(ARMCPU *cpu);
+
 #endif
 
 #endif
-- 
2.3.4