Re: [Qemu-ppc] [PATCH v3 2/3] target-i386: calculate vcpu's TSC rate to be migrated

[Haozhong Zhang]

On Mon, Nov 02, 2015 at 09:40:18AM +0000, James Hogan wrote:
> On Mon, Nov 02, 2015 at 05:26:42PM +0800, Haozhong Zhang wrote:
> > The value of the migrated vcpu's TSC rate is determined as below.
> >  1. If a TSC rate is specified by the cpu option 'tsc-freq', then this
> >     user-specified value will be used.
> >  2. If neither a user-specified TSC rate nor a migrated TSC rate is
> >     present, we will use the TSC rate from KVM (returned by
> >     KVM_GET_TSC_KHZ).
> >  3. Otherwise, we will use the migrated TSC rate.
> > 
> > Signed-off-by: Haozhong Zhang <address@hidden>
> > ---
> >  include/sysemu/kvm.h |  2 ++
> >  kvm-all.c            |  1 +
> >  target-arm/kvm.c     |  5 +++++
> >  target-i386/kvm.c    | 33 +++++++++++++++++++++++++++++++++
> >  target-mips/kvm.c    |  5 +++++
> >  target-ppc/kvm.c     |  5 +++++
> >  target-s390x/kvm.c   |  5 +++++
> >  7 files changed, 56 insertions(+)
> > 
> > diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h
> > index 461ef65..0ec8b98 100644
> > --- a/include/sysemu/kvm.h
> > +++ b/include/sysemu/kvm.h
> > @@ -328,6 +328,8 @@ int kvm_arch_fixup_msi_route(struct 
> > kvm_irq_routing_entry *route,
> >  
> >  int kvm_arch_msi_data_to_gsi(uint32_t data);
> >  
> > +int kvm_arch_setup_tsc_khz(CPUState *cpu);
> > +
> >  int kvm_set_irq(KVMState *s, int irq, int level);
> >  int kvm_irqchip_send_msi(KVMState *s, MSIMessage msg);
> >  
> > diff --git a/kvm-all.c b/kvm-all.c
> > index c442838..1ecaf04 100644
> > --- a/kvm-all.c
> > +++ b/kvm-all.c
> > @@ -1757,6 +1757,7 @@ static void do_kvm_cpu_synchronize_post_init(void 
> > *arg)
> >  {
> >      CPUState *cpu = arg;
> >  
> > +    kvm_arch_setup_tsc_khz(cpu);
> 
> Sorry if this is a stupid question, but why aren't you doing this from
> the i386 kvm_arch_put_registers when level == KVM_PUT_FULL_STATE, rather
> than introducing x86 specifics to the generic KVM api?
> 
> Cheers
> James
>

Yes, I could call kvm_arch_setup_tsc_khz() in kvm_arch_put_registers()
of target-i386 when level == KVM_PUT_FULL_STATE, so that I will not need
to make kvm_arch_setup_tsc_khz() a generic KVM API (which looks weird
for targets other than i386).

Thanks, James!

Haozhong

> >      kvm_arch_put_registers(cpu, KVM_PUT_FULL_STATE);
> >      cpu->kvm_vcpu_dirty = false;
> >  }
> > diff --git a/target-arm/kvm.c b/target-arm/kvm.c
> > index 79ef4c6..a724f6d 100644
> > --- a/target-arm/kvm.c
> > +++ b/target-arm/kvm.c
> > @@ -614,3 +614,8 @@ int kvm_arch_msi_data_to_gsi(uint32_t data)
> >  {
> >      return (data - 32) & 0xffff;
> >  }
> > +
> > +int kvm_arch_setup_tsc_khz(CPUState *cs)
> > +{
> > +    return 0;
> > +}
> > diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> > index 64046cb..aae5e58 100644
> > --- a/target-i386/kvm.c
> > +++ b/target-i386/kvm.c
> > @@ -3034,3 +3034,36 @@ int kvm_arch_msi_data_to_gsi(uint32_t data)
> >  {
> >      abort();
> >  }
> > +
> > +int kvm_arch_setup_tsc_khz(CPUState *cs)
> > +{
> > +    X86CPU *cpu = X86_CPU(cs);
> > +    CPUX86State *env = &cpu->env;
> > +    int r;
> > +
> > +    /*
> > +     * Prepare vcpu's TSC rate to be migrated.
> > +     *
> > +     * - If the user specifies the TSC rate by cpu option 'tsc-freq',
> > +     *   we will use the user-specified value.
> > +     *
> > +     * - If there is neither user-specified TSC rate nor migrated TSC
> > +     *   rate, we will ask KVM for the TSC rate by calling
> > +     *   KVM_GET_TSC_KHZ.
> > +     *
> > +     * - Otherwise, if there is a migrated TSC rate, we will use the
> > +     *   migrated value.
> > +     */
> > +    if (env->tsc_khz) {
> > +        env->tsc_khz_saved = env->tsc_khz;
> > +    } else if (!env->tsc_khz_saved) {
> > +        r = kvm_vcpu_ioctl(cs, KVM_GET_TSC_KHZ);
> > +        if (r < 0) {
> > +            fprintf(stderr, "KVM_GET_TSC_KHZ failed\n");
> > +            return r;
> > +        }
> > +        env->tsc_khz_saved = r;
> > +    }
> > +
> > +    return 0;
> > +}
> > diff --git a/target-mips/kvm.c b/target-mips/kvm.c
> > index 12d7db3..fb26d7e 100644
> > --- a/target-mips/kvm.c
> > +++ b/target-mips/kvm.c
> > @@ -687,3 +687,8 @@ int kvm_arch_msi_data_to_gsi(uint32_t data)
> >  {
> >      abort();
> >  }
> > +
> > +int kvm_arch_setup_tsc_khz(CPUState *cs)
> > +{
> > +    return 0;
> > +}
> > diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c
> > index ac70f08..c429f0c 100644
> > --- a/target-ppc/kvm.c
> > +++ b/target-ppc/kvm.c
> > @@ -2510,3 +2510,8 @@ int kvmppc_enable_hwrng(void)
> >  
> >      return kvmppc_enable_hcall(kvm_state, H_RANDOM);
> >  }
> > +
> > +int kvm_arch_setup_tsc_khz(CPUState *cs)
> > +{
> > +    return 0;
> > +}
> > diff --git a/target-s390x/kvm.c b/target-s390x/kvm.c
> > index c3be180..db5d436 100644
> > --- a/target-s390x/kvm.c
> > +++ b/target-s390x/kvm.c
> > @@ -2248,3 +2248,8 @@ int kvm_arch_msi_data_to_gsi(uint32_t data)
> >  {
> >      abort();
> >  }
> > +
> > +int kvm_arch_setup_tsc_khz(CPUState *cs)
> > +{
> > +    return 0;
> > +}
> > -- 
> > 2.4.8
> >