[Qemu-ppc] [RFC PATCH v4 03/11] cpus: Reclaim vCPU objects

[Bharata B Rao]

From: Gu Zheng <address@hidden>

In order to deal well with the kvm vcpus (which can not be removed without any
protection), we do not close KVM vcpu fd, just record and mark it as stopped
into a list, so that we can reuse it for the appending cpu hot-add request if
possible. It is also the approach that kvm guys suggested:
https://www.mail-archive.com/address@hidden/msg102839.html

Signed-off-by: Chen Fan <address@hidden>
Signed-off-by: Gu Zheng <address@hidden>
Signed-off-by: Zhu Guihua <address@hidden>
Signed-off-by: Bharata B Rao <address@hidden>
               [Explicit CPU_REMOVE() from qemu_kvm/tcg_destroy_vcpu()
                isn't needed as it is done from cpu_exec_exit()]
---
 cpus.c               | 41 +++++++++++++++++++++++++++++++++++++
 include/qom/cpu.h    | 10 +++++++++
 include/sysemu/kvm.h |  1 +
 kvm-all.c            | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++-
 kvm-stub.c           |  5 +++++
 5 files changed, 113 insertions(+), 1 deletion(-)

diff --git a/cpus.c b/cpus.c
index a822ce3..73ae2e7 100644
--- a/cpus.c
+++ b/cpus.c
@@ -888,6 +888,21 @@ void async_run_on_cpu(CPUState *cpu, void (*func)(void 
*data), void *data)
     qemu_cpu_kick(cpu);
 }
 
+static void qemu_kvm_destroy_vcpu(CPUState *cpu)
+{
+    if (kvm_destroy_vcpu(cpu) < 0) {
+        error_report("kvm_destroy_vcpu failed.\n");
+        exit(EXIT_FAILURE);
+    }
+
+    object_unparent(OBJECT(cpu));
+}
+
+static void qemu_tcg_destroy_vcpu(CPUState *cpu)
+{
+    object_unparent(OBJECT(cpu));
+}
+
 static void flush_queued_work(CPUState *cpu)
 {
     struct qemu_work_item *wi;
@@ -982,6 +997,11 @@ static void *qemu_kvm_cpu_thread_fn(void *arg)
             }
         }
         qemu_kvm_wait_io_event(cpu);
+        if (cpu->exit && !cpu_can_run(cpu)) {
+            qemu_kvm_destroy_vcpu(cpu);
+            qemu_mutex_unlock(&qemu_global_mutex);
+            return NULL;
+        }
     }
 
     return NULL;
@@ -1037,6 +1057,7 @@ static void tcg_exec_all(void);
 static void *qemu_tcg_cpu_thread_fn(void *arg)
 {
     CPUState *cpu = arg;
+    CPUState *remove_cpu = NULL;
 
     rcu_register_thread();
 
@@ -1075,6 +1096,16 @@ static void *qemu_tcg_cpu_thread_fn(void *arg)
             }
         }
         qemu_tcg_wait_io_event();
+        CPU_FOREACH(cpu) {
+            if (cpu->exit && !cpu_can_run(cpu)) {
+                remove_cpu = cpu;
+                break;
+            }
+        }
+        if (remove_cpu) {
+            qemu_tcg_destroy_vcpu(remove_cpu);
+            remove_cpu = NULL;
+        }
     }
 
     return NULL;
@@ -1245,6 +1276,13 @@ void resume_all_vcpus(void)
     }
 }
 
+void cpu_remove(CPUState *cpu)
+{
+    cpu->stop = true;
+    cpu->exit = true;
+    qemu_cpu_kick(cpu);
+}
+
 /* For temporary buffers for forming a name */
 #define VCPU_THREAD_NAME_SIZE 16
 
@@ -1437,6 +1475,9 @@ static void tcg_exec_all(void)
                 break;
             }
         } else if (cpu->stop || cpu->stopped) {
+            if (cpu->exit) {
+                next_cpu = CPU_NEXT(cpu);
+            }
             break;
         }
     }
diff --git a/include/qom/cpu.h b/include/qom/cpu.h
index a00e3a8..136d9fe 100644
--- a/include/qom/cpu.h
+++ b/include/qom/cpu.h
@@ -224,6 +224,7 @@ struct kvm_run;
  * @halted: Nonzero if the CPU is in suspended state.
  * @stop: Indicates a pending stop request.
  * @stopped: Indicates the CPU has been artificially stopped.
+ * @exit: Indicates the CPU has exited due to an unplug operation.
  * @tcg_exit_req: Set to force TCG to stop executing linked TBs for this
  *           CPU and return to its top level loop.
  * @singlestep_enabled: Flags for single-stepping.
@@ -267,6 +268,7 @@ struct CPUState {
     bool created;
     bool stop;
     bool stopped;
+    bool exit;
     volatile sig_atomic_t exit_request;
     uint32_t interrupt_request;
     int singlestep_enabled;
@@ -645,6 +647,14 @@ void cpu_exit(CPUState *cpu);
  */
 void cpu_resume(CPUState *cpu);
 
+ /**
+ * cpu_remove:
+ * @cpu: The CPU to remove.
+ *
+ * Requests the CPU to be removed.
+ */
+void cpu_remove(CPUState *cpu);
+
 /**
  * qemu_init_vcpu:
  * @cpu: The vCPU to initialize.
diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
index 983e99e..d53819b 100644
--- a/include/sysemu/kvm.h
+++ b/include/sysemu/kvm.h
@@ -191,6 +191,7 @@ int kvm_has_intx_set_mask(void);
 
 int kvm_init_vcpu(CPUState *cpu);
 int kvm_cpu_exec(CPUState *cpu);
+int kvm_destroy_vcpu(CPUState *cpu);
 
 #ifdef NEED_CPU_H
 
diff --git a/kvm-all.c b/kvm-all.c
index 06e06f2..64a160a 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -59,6 +59,12 @@
 
 #define KVM_MSI_HASHTAB_SIZE    256
 
+struct KVMParkedVcpu {
+    unsigned long vcpu_id;
+    int kvm_fd;
+    QLIST_ENTRY(KVMParkedVcpu) node;
+};
+
 struct KVMState
 {
     AccelState parent_obj;
@@ -95,6 +101,7 @@ struct KVMState
     bool direct_msi;
 #endif
     KVMMemoryListener memory_listener;
+    QLIST_HEAD(, KVMParkedVcpu) kvm_parked_vcpus;
 };
 
 KVMState *kvm_state;
@@ -235,6 +242,53 @@ static int kvm_set_user_memory_region(KVMMemoryListener 
*kml, KVMSlot *slot)
     return kvm_vm_ioctl(s, KVM_SET_USER_MEMORY_REGION, &mem);
 }
 
+int kvm_destroy_vcpu(CPUState *cpu)
+{
+    KVMState *s = kvm_state;
+    long mmap_size;
+    struct KVMParkedVcpu *vcpu = NULL;
+    int ret = 0;
+
+    DPRINTF("kvm_destroy_vcpu\n");
+
+    mmap_size = kvm_ioctl(s, KVM_GET_VCPU_MMAP_SIZE, 0);
+    if (mmap_size < 0) {
+        ret = mmap_size;
+        DPRINTF("KVM_GET_VCPU_MMAP_SIZE failed\n");
+        goto err;
+    }
+
+    ret = munmap(cpu->kvm_run, mmap_size);
+    if (ret < 0) {
+        goto err;
+    }
+
+    vcpu = g_malloc0(sizeof(*vcpu));
+    vcpu->vcpu_id = kvm_arch_vcpu_id(cpu);
+    vcpu->kvm_fd = cpu->kvm_fd;
+    QLIST_INSERT_HEAD(&kvm_state->kvm_parked_vcpus, vcpu, node);
+err:
+    return ret;
+}
+
+static int kvm_get_vcpu(KVMState *s, unsigned long vcpu_id)
+{
+    struct KVMParkedVcpu *cpu;
+
+    QLIST_FOREACH(cpu, &s->kvm_parked_vcpus, node) {
+        if (cpu->vcpu_id == vcpu_id) {
+            int kvm_fd;
+
+            QLIST_REMOVE(cpu, node);
+            kvm_fd = cpu->kvm_fd;
+            g_free(cpu);
+            return kvm_fd;
+        }
+    }
+
+    return kvm_vm_ioctl(s, KVM_CREATE_VCPU, (void *)vcpu_id);
+}
+
 int kvm_init_vcpu(CPUState *cpu)
 {
     KVMState *s = kvm_state;
@@ -243,7 +297,7 @@ int kvm_init_vcpu(CPUState *cpu)
 
     DPRINTF("kvm_init_vcpu\n");
 
-    ret = kvm_vm_ioctl(s, KVM_CREATE_VCPU, (void *)kvm_arch_vcpu_id(cpu));
+    ret = kvm_get_vcpu(s, kvm_arch_vcpu_id(cpu));
     if (ret < 0) {
         DPRINTF("kvm_create_vcpu failed\n");
         goto err;
@@ -1469,6 +1523,7 @@ static int kvm_init(MachineState *ms)
 #ifdef KVM_CAP_SET_GUEST_DEBUG
     QTAILQ_INIT(&s->kvm_sw_breakpoints);
 #endif
+    QLIST_INIT(&s->kvm_parked_vcpus);
     s->vmfd = -1;
     s->fd = qemu_open("/dev/kvm", O_RDWR);
     if (s->fd == -1) {
diff --git a/kvm-stub.c b/kvm-stub.c
index d9ad624..4b3ba8c 100644
--- a/kvm-stub.c
+++ b/kvm-stub.c
@@ -31,6 +31,11 @@ bool kvm_gsi_direct_mapping;
 bool kvm_allowed;
 bool kvm_readonly_mem_allowed;
 
+int kvm_destroy_vcpu(CPUState *cpu)
+{
+    return -ENOSYS;
+}
+
 int kvm_init_vcpu(CPUState *cpu)
 {
     return -ENOSYS;
-- 
2.1.0