Re: [Qemu-devel] [PATCH 03/16] introduce resume_vcpu(), for single CPU

[Igor Mammedov <imammedo@redhat.com>]

On Mon, 22 Apr 2013 13:59:17 +0300
Gleb Natapov <gleb@redhat.com> wrote:

> On Mon, Apr 22, 2013 at 12:54:04PM +0200, Igor Mammedov wrote:
> > On Mon, 22 Apr 2013 13:40:02 +0300
> > Gleb Natapov <gleb@redhat.com> wrote:
> > 
> > > On Tue, Apr 16, 2013 at 12:12:43AM +0200, Igor Mammedov wrote:
> > > > ... also add stub for it, to make possible to use it in qom/cpu.c,
> > > > which is shared with user emulators.
> > > > 
> > > > Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> > > > ---
> > > > Note:
> > > >   it will be re-used from qom/cpu.c by hotpluged CPU
> > > > ---
> > > >  cpus.c              | 11 ++++++++---
> > > >  include/qom/cpu.h   |  9 +++++++++
> > > >  stubs/Makefile.objs |  1 +
> > > >  stubs/cpus.c        |  5 +++++
> > > >  4 files changed, 23 insertions(+), 3 deletions(-)
> > > >  create mode 100644 stubs/cpus.c
> > > > 
> > > > diff --git a/cpus.c b/cpus.c
> > > > index c15ff6c..c347db5 100644
> > > > --- a/cpus.c
> > > > +++ b/cpus.c
> > > > @@ -993,6 +993,13 @@ void pause_all_vcpus(void)
> > > >      }
> > > >  }
> > > >  
> > > > +void resume_vcpu(CPUState *cpu)
> > > > +{
> > > > +    cpu->stop = false;
> > > > +    cpu->stopped = false;
> > > > +    qemu_cpu_kick(cpu);
> > > > +}
> > > > +
> > > >  void resume_all_vcpus(void)
> > > >  {
> > > >      CPUArchState *penv = first_cpu;
> > > > @@ -1000,9 +1007,7 @@ void resume_all_vcpus(void)
> > > >      qemu_clock_enable(vm_clock, true);
> > > >      while (penv) {
> > > >          CPUState *pcpu = ENV_GET_CPU(penv);
> > > > -        pcpu->stop = false;
> > > > -        pcpu->stopped = false;
> > > > -        qemu_cpu_kick(pcpu);
> > > > +        resume_vcpu(pcpu);
> > > >          penv = penv->next_cpu;
> > > >      }
> > > >  }
> > > > diff --git a/include/qom/cpu.h b/include/qom/cpu.h
> > > > index 3664a1b..6ce6f10 100644
> > > > --- a/include/qom/cpu.h
> > > > +++ b/include/qom/cpu.h
> > > > @@ -256,5 +256,14 @@ void cpu_interrupt(CPUState *cpu, int mask);
> > > >   */
> > > >  void cpu_reset_interrupt(CPUState *cpu, int mask);
> > > >  
> > > > +/**
> > > > + * resume_vcpu:
> > > > + * @cpu: The CPU to resume.
> > > > + *
> > > > + * Resumes CPU, i.e. puts CPU into runable state.
> > > > + * KVM requires extra call cpu_synchronize_post_init() to make
> > > > + * KVM's CPU instance runable.
> > > > + */
> > > Can you elaborate on this a bit. Why is it needed and why is it relevant
> > > for this function?
> > If running in KVM mode and resume_vcpu() is called without
> > cpu_synchronize_post_init(), then CPU instance in KVM will be
> > left in UNCONFIGURED state. I've added comment here to document 
> > that resume_vcpu() isn't enough to make CPU run-able in case of KVM.
> > 
> But this really relevant only during vcpu creation after that
> resume_vcpu() should just work. My be have launch_vcpu() function that
Agreed, it's applicable only during CPU creation.

> does the right thing and add assert to resume_vcpu() if it is called on
> vcpu that is not launched yet. In other words made the dependency clear
> in the code, not comment.
Would dropping this comment, suffice
and re-factoring to use launch_vcpu() done later?

> --
> 			Gleb.