Re: [Qemu-devel] [PATCH v3 2/7] qom/cpu: move register_vmstate to common CPUClass.realizefn

[Chen Fan]

On 01/29/2015 10:04 PM, Igor Mammedov wrote:
> On Wed, 14 Jan 2015 15:27:25 +0800
> Zhu Guihua <address@hidden> wrote:
>
> > From: Gu Zheng <address@hidden>
> >
> > Move cpu vmstate register from cpu_exec_init into cpu_common_realizefn,
> > and use cc->get_arch_id as the instance id that suggested by Igor to
> > fix the migration issue.
> >
> > Signed-off-by: Gu Zheng <address@hidden>
> > Signed-off-by: Zhu Guihua <address@hidden>
> > ---
> >   exec.c            | 32 +++++++++++++++++++-------------
> >   include/qom/cpu.h |  2 ++
> >   qom/cpu.c         |  2 ++
> >   3 files changed, 23 insertions(+), 13 deletions(-)
> >
> > diff --git a/exec.c b/exec.c
> > index 081818e..c9ffda6 100644
> > --- a/exec.c
> > +++ b/exec.c
> > @@ -513,10 +513,28 @@ void tcg_cpu_address_space_init(CPUState *cpu, 
> > AddressSpace *as)
> >   }
> >   #endif
> >   
> > +void cpu_vmstate_register(CPUState *cpu)
> > +{
> > +    CPUClass *cc = CPU_GET_CLASS(cpu);
> > +    int cpu_index = cc->get_arch_id(cpu);
> that probable would be source migration problems:
> because cc->get_arch_id(cpu) depending on topology might
> be not sequential, for example: sockets=4,core=3
> that would create sparse APIC numbering.
>
> as result migration from old qemu to one with this change
> would be rejected due to vmsd id mismatch mismatch.
>
> we need a better way to handle cross version migration
> between old/new scheme.
Hi Igor,

    I think to handler cross version migration issue, we only
need to do is converting new 'apic-id' to old 'cpu_index' to match
vmsd id  between old to new scheme.
we can save old cpu_index in alias id. and in order to keep
instance_id differ from alias id. we can use apic_id + maxcpus
as the instance_id. so during migration we can find the corresponding
cpu with instance_id regardless new/old scheme.

I has made a patch and test migrating from old version to new version.
it seems work fine. pls have a look at the attach file. ;)

Thanks,
Chen

> > +
> > +    if (qdev_get_vmsd(DEVICE(cpu)) == NULL) {
> > +        vmstate_register(NULL, cpu_index, &vmstate_cpu_common, cpu);
> > +    }
> > +#if defined(CPU_SAVE_VERSION) && !defined(CONFIG_USER_ONLY)
> that ifdef block affects only sparc/mips/cris and builds target specific code
> while you are trying to call it from target independent qom/cpu.c
>
> I'd suggest leave it where it was or better move into respective
> targets realize_fns
>
> > +    register_savevm(NULL, "cpu", cpu_index, CPU_SAVE_VERSION,
> > +                    cpu_save, cpu_load, cpu->env_ptr);
> > +    assert(cc->vmsd == NULL);
> > +    assert(qdev_get_vmsd(DEVICE(cpu)) == NULL);
> > +#endif
> > +    if (cc->vmsd != NULL) {
> > +        vmstate_register(NULL, cpu_index, cc->vmsd, cpu);
> > +    }
> > +}
> > +
> >   void cpu_exec_init(CPUArchState *env)
> >   {
> >       CPUState *cpu = ENV_GET_CPU(env);
> > -    CPUClass *cc = CPU_GET_CLASS(cpu);
> >       CPUState *some_cpu;
> >       int cpu_index;
> >   
> > @@ -539,18 +557,6 @@ void cpu_exec_init(CPUArchState *env)
> >   #if defined(CONFIG_USER_ONLY)
> >       cpu_list_unlock();
> >   #endif
> > -    if (qdev_get_vmsd(DEVICE(cpu)) == NULL) {
> > -        vmstate_register(NULL, cpu_index, &vmstate_cpu_common, cpu);
> > -    }
> > -#if defined(CPU_SAVE_VERSION) && !defined(CONFIG_USER_ONLY)
> > -    register_savevm(NULL, "cpu", cpu_index, CPU_SAVE_VERSION,
> > -                    cpu_save, cpu_load, env);
> > -    assert(cc->vmsd == NULL);
> > -    assert(qdev_get_vmsd(DEVICE(cpu)) == NULL);
> > -#endif
> > -    if (cc->vmsd != NULL) {
> > -        vmstate_register(NULL, cpu_index, cc->vmsd, cpu);
> > -    }
> And in general do CONFIG_USER_ONLY targets actually need/use
> migration code?
>
> >   }
> >   
> >   #if defined(TARGET_HAS_ICE)
> > diff --git a/include/qom/cpu.h b/include/qom/cpu.h
> > index 2098f1c..936afcd 100644
> > --- a/include/qom/cpu.h
> > +++ b/include/qom/cpu.h
> > @@ -562,6 +562,8 @@ void cpu_interrupt(CPUState *cpu, int mask);
> >   
> >   #endif /* USER_ONLY */
> >   
> > +void cpu_vmstate_register(CPUState *cpu);
> > +
> >   #ifdef CONFIG_SOFTMMU
> >   static inline void cpu_unassigned_access(CPUState *cpu, hwaddr addr,
> >                                            bool is_write, bool is_exec,
> > diff --git a/qom/cpu.c b/qom/cpu.c
> > index 9c68fa4..a639822 100644
> > --- a/qom/cpu.c
> > +++ b/qom/cpu.c
> > @@ -302,6 +302,8 @@ static void cpu_common_realizefn(DeviceState *dev, Error 
> > **errp)
> >   {
> >       CPUState *cpu = CPU(dev);
> >   
> > +    cpu_vmstate_register(cpu);
> > +
> >       if (dev->hotplugged) {
> >           cpu_synchronize_post_init(cpu);
> >           cpu_resume(cpu);
> .

fix-cross-version-impact.diff
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