Re: [Qemu-devel] [RFC PATCH v1 10/13] cpus, spapr: reclaim allocated vCPU objects

[David Gibson]

On Thu, Jan 08, 2015 at 11:40:17AM +0530, Bharata B Rao wrote:
> From: Gu Zheng <address@hidden>

This needs a commit message, it's not at all clear from the 1-line description.

> 
> Signed-off-by: Gu Zheng <address@hidden>
> Signed-off-by: Bharata B Rao <address@hidden>
>                (added spapr bits)
> ---
>  cpus.c               | 44 ++++++++++++++++++++++++++++++++++++++++
>  hw/ppc/spapr.c       | 14 ++++++++++++-
>  include/qom/cpu.h    | 11 ++++++++++
>  include/sysemu/kvm.h |  1 +
>  kvm-all.c            | 57 
> +++++++++++++++++++++++++++++++++++++++++++++++++++-
>  5 files changed, 125 insertions(+), 2 deletions(-)

The generic and PAPR specific parts should probably be divided into
different patches, since they'll want to go via different trees.

> diff --git a/cpus.c b/cpus.c
> index 1b5168a..98b7199 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -871,6 +871,24 @@ 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;
> @@ -964,6 +982,11 @@ 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;
> @@ -1018,6 +1041,7 @@ 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);
> @@ -1052,6 +1076,16 @@ 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;
> @@ -1208,6 +1242,13 @@ 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
>  
> @@ -1402,6 +1443,9 @@ 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/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index ec793b1..44405b2 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1910,7 +1910,19 @@ static void spapr_cpu_hotplug_add(DeviceState *dev, 
> CPUState *cs)
>  
>  static void spapr_cpu_release(DeviceState *dev, void *opaque)
>  {
> -    /* Release vCPU */
> +    CPUState *cs;
> +    int i;
> +    int id = ppc_get_vcpu_dt_id(POWERPC_CPU(CPU(dev)));
> +
> +    for (i = id; i < id + smp_threads; i++) {
> +        CPU_FOREACH(cs) {
> +            PowerPCCPU *cpu = POWERPC_CPU(cs);
> +
> +            if (i == ppc_get_vcpu_dt_id(cpu)) {
> +                cpu_remove(cs);
> +            }
> +        }
> +    }
>  }
>  
>  static void spapr_cpu_hotplug_remove(DeviceState *dev, CPUState *cs)
> diff --git a/include/qom/cpu.h b/include/qom/cpu.h
> index 2098f1c..30fd0cd 100644
> --- a/include/qom/cpu.h
> +++ b/include/qom/cpu.h
> @@ -206,6 +206,7 @@ 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.
> @@ -249,6 +250,7 @@ struct CPUState {
>      bool created;
>      bool stop;
>      bool stopped;
> +    bool exit;
>      volatile sig_atomic_t exit_request;
>      uint32_t interrupt_request;
>      int singlestep_enabled;
> @@ -305,6 +307,7 @@ struct CPUState {
>  QTAILQ_HEAD(CPUTailQ, CPUState);
>  extern struct CPUTailQ cpus;
>  #define CPU_NEXT(cpu) QTAILQ_NEXT(cpu, node)
> +#define CPU_REMOVE(cpu) QTAILQ_REMOVE(&cpus, cpu, node)
>  #define CPU_FOREACH(cpu) QTAILQ_FOREACH(cpu, &cpus, node)
>  #define CPU_FOREACH_SAFE(cpu, next_cpu) \
>      QTAILQ_FOREACH_SAFE(cpu, &cpus, node, next_cpu)
> @@ -610,6 +613,14 @@ 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 104cf35..da064c1 100644
> --- a/include/sysemu/kvm.h
> +++ b/include/sysemu/kvm.h
> @@ -186,6 +186,7 @@ int kvm_has_gsi_routing(void);
>  int kvm_has_intx_set_mask(void);
>  
>  int kvm_init_vcpu(CPUState *cpu);
> +int kvm_destroy_vcpu(CPUState *cpu);
>  int kvm_cpu_exec(CPUState *cpu);
>  
>  #ifdef NEED_CPU_H
> diff --git a/kvm-all.c b/kvm-all.c
> index 18cc6b4..6f543ce 100644
> --- a/kvm-all.c
> +++ b/kvm-all.c
> @@ -71,6 +71,12 @@ typedef struct KVMSlot
>  
>  typedef struct kvm_dirty_log KVMDirtyLog;
>  
> +struct KVMParkedVcpu {
> +    unsigned long vcpu_id;
> +    int kvm_fd;
> +    QLIST_ENTRY(KVMParkedVcpu) node;
> +};
> +
>  struct KVMState
>  {
>      AccelState parent_obj;
> @@ -107,6 +113,7 @@ struct KVMState
>      QTAILQ_HEAD(msi_hashtab, KVMMSIRoute) msi_hashtab[KVM_MSI_HASHTAB_SIZE];
>      bool direct_msi;
>  #endif
> +    QLIST_HEAD(, KVMParkedVcpu) kvm_parked_vcpus;
>  };
>  
>  #define TYPE_KVM_ACCEL ACCEL_CLASS_NAME("kvm")
> @@ -247,6 +254,53 @@ 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");
> +
> +    mmap_size = kvm_ioctl(s, KVM_GET_VCPU_MMAP_SIZE, 0);
> +    if (mmap_size < 0) {
> +        ret = mmap_size;
> +        DPRINTF("kvm_destroy_vcpu 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);

What's the reason for parking vcpus rather than removing / recreating
them at the kvm level?

> +
> +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;
> @@ -255,7 +309,7 @@ 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;
> @@ -1441,6 +1495,7 @@ 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) {

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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