Re: [Qemu-devel] [RFC V2 10/10] cpus: reclaim allocated vCPU objects

[Igor Mammedov <imammedo@redhat.com>]

On Thu, 28 Aug 2014 11:36:42 +0800
Gu Zheng <guz.fnst@cn.fujitsu.com> wrote:

> After ACPI get a signal to eject a vCPU, the vCPU must be
> removed from CPU list，before the vCPU really removed,  then
> release the all related vCPU objects.
> But we do not close KVM vcpu fd, just record it into a list, in
> order to reuse it.
> 
> Signed-off-by: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
> Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
> ---
>  cpus.c               |   37 ++++++++++++++++++++++++++++++++
>  include/sysemu/kvm.h |    1 +
>  kvm-all.c            |   57 +++++++++++++++++++++++++++++++++++++++++++++++++-
>  3 files changed, 94 insertions(+), 1 deletions(-)
> 
> diff --git a/cpus.c b/cpus.c
> index eee693b..0608b41 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -851,6 +851,24 @@ 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)
> +{
> +    CPU_REMOVE(cpu);
> +
> +    if (kvm_destroy_vcpu(cpu) < 0) {
> +        fprintf(stderr, "kvm_destroy_vcpu failed.\n");
> +        exit(1);
> +    }
> +
> +    object_unparent(OBJECT(cpu));
> +}
> +
> +static void qemu_tcg_destroy_vcpu(CPUState *cpu)
> +{
> +    CPU_REMOVE(cpu);
> +    object_unparent(OBJECT(cpu));
> +}
> +
>  static void flush_queued_work(CPUState *cpu)
>  {
>      struct qemu_work_item *wi;
> @@ -942,6 +960,11 @@ 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;
> @@ -994,6 +1017,7 @@ static void tcg_exec_all(void);
>  static void *qemu_tcg_cpu_thread_fn(void *arg)
>  {
>      CPUState *cpu = arg;
> +    CPUState *remove_cpu = NULL;
>  
>      qemu_tcg_init_cpu_signals();
>      qemu_thread_get_self(cpu->thread);
> @@ -1026,6 +1050,16 @@ 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;
> @@ -1383,6 +1417,9 @@ 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/sysemu/kvm.h b/include/sysemu/kvm.h
> index 174ea36..88e2403 100644
> --- a/include/sysemu/kvm.h
> +++ b/include/sysemu/kvm.h
> @@ -178,6 +178,7 @@ 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 1402f4f..d0caeff 100644
> --- a/kvm-all.c
> +++ b/kvm-all.c
> @@ -74,6 +74,12 @@ typedef struct KVMSlot
>  
>  typedef struct kvm_dirty_log KVMDirtyLog;
>  
> +struct KVMParkedVcpu {
> +    unsigned long vcpu_id;
> +    int kvm_fd;
> +    QLIST_ENTRY(KVMParkedVcpu) node;
> +};
> +
>  struct KVMState
>  {
>      KVMSlot *slots;
> @@ -108,6 +114,7 @@ struct KVMState
>      QTAILQ_HEAD(msi_hashtab, KVMMSIRoute) msi_hashtab[KVM_MSI_HASHTAB_SIZE];
>      bool direct_msi;
>  #endif
> +    QLIST_HEAD(, KVMParkedVcpu) kvm_parked_vcpus;
>  };
>  
>  KVMState *kvm_state;
> @@ -226,6 +233,53 @@ static int kvm_set_user_memory_region(KVMState *s, 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");
maybe it would be good to put cpu in RESET state before parking it?

Do we need a kernel patch to park VCPU so it wouldn't be possible
to wake it up by sending INIT/SIPI to it?

> +
> +    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;
> @@ -234,7 +288,7 @@ 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;
> @@ -1404,6 +1458,7 @@ int kvm_init(MachineClass *mc)
>  #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) {