Re: [Qemu-devel] [PATCH v2 1/2] move vm_start to cpus.c

[Claudio Imbrenda]

On 27/01/17 18:05, Alex Bennée wrote:
> 
> Claudio Imbrenda <address@hidden> writes:
> 
>> On 27/01/17 17:31, Alex Bennée wrote:
>>>
>>> Claudio Imbrenda <address@hidden> writes:
>>>
>>>> This patch:
>>>>
>>>> * moves vm_start to cpus.c .
>>>> * exports qemu_vmstop_requested, since it's needed by vm_start .
>>>> * extracts vm_prepare_start from vm_start; it does what vm_start did,
>>>>   except restarting the cpus. vm_start now calls vm_prepare_start.
>>>> * moves the call to qemu_clock_enable away from resume_all_vcpus, and
>>>>   add an explicit call to it before each instance of resume_all_vcpus
>>>>   in the code.
>>>
>>> Can you be a bit more explicit about this? Shouldn't CPU time still
>>> accrue even if you are only starting some of them?
>>
>> This is what's happening in the newest version of this patch, which I
>> sent around yesterday, although I forgot to update the patch
>> description; I'll send a fixed version ASAP.
>>
>>> I'd prefer making resume_all_vcpus() a private function called from
>>
>> resume_all_vcpus is already being used in other files too, doesn't make
>> sense to make it private now.
> 
> Yeah I would rename the call-sites across QEMU. Perhaps just one entry
> point of rename_vcpus() which does the right thing given a list or NULL.
> But pushing the details of restarting the timer to the call sites just

this is not happening any longer in the patch I sent yesterday (v6).
the only thing happening now in the first patch is moving vm_start and
splitting it. clocks are not affected, no further code changes are needed.

> sounds like a way of it getting missed next time someone adds a resume
> somewhere.
> 
>>
>>> resume_some_vcpus() which can then make the QEMU_CLOCK_VIRTUAL decision
>>> in one place - with a comment.
>>>
>>>> * adds resume_some_vcpus, to selectively restart only some CPUs.
>>>>
>>>> Signed-off-by: Claudio Imbrenda <address@hidden>
>>>> ---
>>>>  cpus.c                     | 61 
>>>> +++++++++++++++++++++++++++++++++++++++++++++-
>>>>  hw/i386/kvmvapic.c         |  2 ++
>>>>  include/sysemu/cpus.h      |  1 +
>>>>  include/sysemu/sysemu.h    |  2 ++
>>>>  target-s390x/misc_helper.c |  2 ++
>>>>  vl.c                       | 32 +++---------------------
>>>>  6 files changed, 70 insertions(+), 30 deletions(-)
>>>>
>>>> diff --git a/cpus.c b/cpus.c
>>>> index 31204bb..c102624 100644
>>>> --- a/cpus.c
>>>> +++ b/cpus.c
>>>> @@ -1260,12 +1260,28 @@ void resume_all_vcpus(void)
>>>>  {
>>>>      CPUState *cpu;
>>>>
>>>> -    qemu_clock_enable(QEMU_CLOCK_VIRTUAL, true);
>>>>      CPU_FOREACH(cpu) {
>>>>          cpu_resume(cpu);
>>>>      }
>>>>  }
>>>>
>>>> +/**
>>>> + * resume_some_vcpus - resumes some vCPUs, indicated in a NULL-terminated
>>>> + * array of CPUState *; if the parameter is NULL, all CPUs are resumed.
>>>> + */
>>>> +void resume_some_vcpus(CPUState **cpus)
>>>> +{
>>>> +    int idx;
>>>> +
>>>> +    if (!cpus) {
>>>> +        resume_all_vcpus();
>>>> +        return;
>>>> +    }
>>>> +    for (idx = 0; cpus[idx]; idx++) {
>>>> +        cpu_resume(cpus[idx]);
>>>> +    }
>>>> +}
>>>> +
>>>>  void cpu_remove(CPUState *cpu)
>>>>  {
>>>>      cpu->stop = true;
>>>> @@ -1396,6 +1412,49 @@ int vm_stop(RunState state)
>>>>      return do_vm_stop(state);
>>>>  }
>>>>
>>>> +/**
>>>> + * Prepare for (re)starting the VM.
>>>> + * Returns -1 if the vCPUs are not to be restarted (e.g. if they are 
>>>> already
>>>> + * running or in case of an error condition), 0 otherwise.
>>>> + */
>>>> +int vm_prepare_start(void)
>>>> +{
>>>> +    RunState requested;
>>>> +    int res = 0;
>>>> +
>>>> +    qemu_vmstop_requested(&requested);
>>>> +    if (runstate_is_running() && requested == RUN_STATE__MAX) {
>>>> +        return -1;
>>>> +    }
>>>> +
>>>> +    /* Ensure that a STOP/RESUME pair of events is emitted if a
>>>> +     * vmstop request was pending.  The BLOCK_IO_ERROR event, for
>>>> +     * example, according to documentation is always followed by
>>>> +     * the STOP event.
>>>> +     */
>>>> +    if (runstate_is_running()) {
>>>> +        qapi_event_send_stop(&error_abort);
>>>> +        res = -1;
>>>> +    } else {
>>>> +        replay_enable_events();
>>>> +        cpu_enable_ticks();
>>>> +        runstate_set(RUN_STATE_RUNNING);
>>>> +        vm_state_notify(1, RUN_STATE_RUNNING);
>>>> +    }
>>>> +
>>>> +    /* XXX: is it ok to send this even before actually resuming the CPUs? 
>>>> */
>>>> +    qapi_event_send_resume(&error_abort);
>>>> +    return res;
>>>> +}
>>>> +
>>>> +void vm_start(void)
>>>> +{
>>>> +    if (!vm_prepare_start()) {
>>>> +        qemu_clock_enable(QEMU_CLOCK_VIRTUAL, true);
>>>> +        resume_all_vcpus();
>>>> +    }
>>>> +}
>>>> +
>>>>  /* does a state transition even if the VM is already stopped,
>>>>     current state is forgotten forever */
>>>>  int vm_stop_force_state(RunState state)
>>>> diff --git a/hw/i386/kvmvapic.c b/hw/i386/kvmvapic.c
>>>> index 74a549b..3101860 100644
>>>> --- a/hw/i386/kvmvapic.c
>>>> +++ b/hw/i386/kvmvapic.c
>>>> @@ -446,6 +446,7 @@ static void patch_instruction(VAPICROMState *s, X86CPU 
>>>> *cpu, target_ulong ip)
>>>>          abort();
>>>>      }
>>>>
>>>> +    qemu_clock_enable(QEMU_CLOCK_VIRTUAL, true);
>>>>      resume_all_vcpus();
>>>>
>>>>      if (!kvm_enabled()) {
>>>> @@ -686,6 +687,7 @@ static void vapic_write(void *opaque, hwaddr addr, 
>>>> uint64_t data,
>>>>              pause_all_vcpus();
>>>>              patch_byte(cpu, env->eip - 2, 0x66);
>>>>              patch_byte(cpu, env->eip - 1, 0x90);
>>>> +            qemu_clock_enable(QEMU_CLOCK_VIRTUAL, true);
>>>>              resume_all_vcpus();
>>>>          }
>>>>
>>>> diff --git a/include/sysemu/cpus.h b/include/sysemu/cpus.h
>>>> index 3728a1e..5fa074b 100644
>>>> --- a/include/sysemu/cpus.h
>>>> +++ b/include/sysemu/cpus.h
>>>> @@ -5,6 +5,7 @@
>>>>  bool qemu_in_vcpu_thread(void);
>>>>  void qemu_init_cpu_loop(void);
>>>>  void resume_all_vcpus(void);
>>>> +void resume_some_vcpus(CPUState **cpus);
>>>>  void pause_all_vcpus(void);
>>>>  void cpu_stop_current(void);
>>>>  void cpu_ticks_init(void);
>>>> diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
>>>> index ef2c50b..ac301d6 100644
>>>> --- a/include/sysemu/sysemu.h
>>>> +++ b/include/sysemu/sysemu.h
>>>> @@ -37,6 +37,7 @@ void vm_state_notify(int running, RunState state);
>>>>  #define VMRESET_REPORT   true
>>>>
>>>>  void vm_start(void);
>>>> +int vm_prepare_start(void);
>>>>  int vm_stop(RunState state);
>>>>  int vm_stop_force_state(RunState state);
>>>>
>>>> @@ -60,6 +61,7 @@ void qemu_register_powerdown_notifier(Notifier 
>>>> *notifier);
>>>>  void qemu_system_debug_request(void);
>>>>  void qemu_system_vmstop_request(RunState reason);
>>>>  void qemu_system_vmstop_request_prepare(void);
>>>> +bool qemu_vmstop_requested(RunState *r);
>>>>  int qemu_shutdown_requested_get(void);
>>>>  int qemu_reset_requested_get(void);
>>>>  void qemu_system_killed(int signal, pid_t pid);
>>>> diff --git a/target-s390x/misc_helper.c b/target-s390x/misc_helper.c
>>>> index 4df2ec6..2b74710 100644
>>>> --- a/target-s390x/misc_helper.c
>>>> +++ b/target-s390x/misc_helper.c
>>>> @@ -133,6 +133,7 @@ static int modified_clear_reset(S390CPU *cpu)
>>>>      s390_crypto_reset();
>>>>      scc->load_normal(CPU(cpu));
>>>>      cpu_synchronize_all_post_reset();
>>>> +    qemu_clock_enable(QEMU_CLOCK_VIRTUAL, true);
>>>>      resume_all_vcpus();
>>>>      return 0;
>>>>  }
>>>> @@ -152,6 +153,7 @@ static int load_normal_reset(S390CPU *cpu)
>>>>      scc->initial_cpu_reset(CPU(cpu));
>>>>      scc->load_normal(CPU(cpu));
>>>>      cpu_synchronize_all_post_reset();
>>>> +    qemu_clock_enable(QEMU_CLOCK_VIRTUAL, true);
>>>>      resume_all_vcpus();
>>>>      return 0;
>>>>  }
>>>> diff --git a/vl.c b/vl.c
>>>> index f3abd99..42addbb 100644
>>>> --- a/vl.c
>>>> +++ b/vl.c
>>>> @@ -746,7 +746,7 @@ StatusInfo *qmp_query_status(Error **errp)
>>>>      return info;
>>>>  }
>>>>
>>>> -static bool qemu_vmstop_requested(RunState *r)
>>>> +bool qemu_vmstop_requested(RunState *r)
>>>>  {
>>>>      qemu_mutex_lock(&vmstop_lock);
>>>>      *r = vmstop_requested;
>>>> @@ -767,34 +767,6 @@ void qemu_system_vmstop_request(RunState state)
>>>>      qemu_notify_event();
>>>>  }
>>>>
>>>> -void vm_start(void)
>>>> -{
>>>> -    RunState requested;
>>>> -
>>>> -    qemu_vmstop_requested(&requested);
>>>> -    if (runstate_is_running() && requested == RUN_STATE__MAX) {
>>>> -        return;
>>>> -    }
>>>> -
>>>> -    /* Ensure that a STOP/RESUME pair of events is emitted if a
>>>> -     * vmstop request was pending.  The BLOCK_IO_ERROR event, for
>>>> -     * example, according to documentation is always followed by
>>>> -     * the STOP event.
>>>> -     */
>>>> -    if (runstate_is_running()) {
>>>> -        qapi_event_send_stop(&error_abort);
>>>> -    } else {
>>>> -        replay_enable_events();
>>>> -        cpu_enable_ticks();
>>>> -        runstate_set(RUN_STATE_RUNNING);
>>>> -        vm_state_notify(1, RUN_STATE_RUNNING);
>>>> -        resume_all_vcpus();
>>>> -    }
>>>> -
>>>> -    qapi_event_send_resume(&error_abort);
>>>> -}
>>>> -
>>>> -
>>>>  /***********************************************************/
>>>>  /* real time host monotonic timer */
>>>>
>>>> @@ -1910,6 +1882,7 @@ static bool main_loop_should_exit(void)
>>>>      if (qemu_reset_requested()) {
>>>>          pause_all_vcpus();
>>>>          qemu_system_reset(VMRESET_REPORT);
>>>> +        qemu_clock_enable(QEMU_CLOCK_VIRTUAL, true);
>>>>          resume_all_vcpus();
>>>>          if (!runstate_check(RUN_STATE_RUNNING) &&
>>>>                  !runstate_check(RUN_STATE_INMIGRATE)) {
>>>> @@ -1921,6 +1894,7 @@ static bool main_loop_should_exit(void)
>>>>          qemu_system_reset(VMRESET_SILENT);
>>>>          notifier_list_notify(&wakeup_notifiers, &wakeup_reason);
>>>>          wakeup_reason = QEMU_WAKEUP_REASON_NONE;
>>>> +        qemu_clock_enable(QEMU_CLOCK_VIRTUAL, true);
>>>>          resume_all_vcpus();
>>>>          qapi_event_send_wakeup(&error_abort);
>>>>      }
>>>
>>>
>>> --
>>> Alex Bennée
>>>
> 
> 
> --
> Alex Bennée
>