Re: [Qemu-devel] [PATCH v5 1/3] target-i386: fallback vcpu's TSC rate to value returned by KVM

[Haozhong Zhang]

On 11/17/15 11:14, Eduardo Habkost wrote:
> On Tue, Nov 17, 2015 at 01:20:37PM +0800, Haozhong Zhang wrote:
> > If no user-specified TSC rate is present, we will try to set
> > env->tsc_khz to the value returned by KVM_GET_TSC_KHZ.
> > 
> > Signed-off-by: Haozhong Zhang <address@hidden>
> > ---
> >  target-i386/kvm.c | 12 ++++++++++++
> >  1 file changed, 12 insertions(+)
> > 
> > diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> > index 2a9953b..9e4d27f 100644
> > --- a/target-i386/kvm.c
> > +++ b/target-i386/kvm.c
> > @@ -832,6 +832,18 @@ int kvm_arch_init_vcpu(CPUState *cs)
> >          }
> >      }
> >  
> > +    /*
> > +     * If no user-specified TSC frequency is present, we will try to
> > +     * set env->tsc_khz to the value used by KVM.
> > +     */
> 
> If you send a new version of this series, please to describe
> "why", not "what". We can see in the code that we are setting
> env->tsc to the value used by KVM, but the comment need to
> explain why.
>

I'll update comments in the next version.

Haozhong

> > +    if (!env->tsc_khz) {
> > +        r = kvm_check_extension(cs->kvm_state, KVM_CAP_GET_TSC_KHZ) ?
> > +            kvm_vcpu_ioctl(cs, KVM_GET_TSC_KHZ) : -ENOTSUP;
> > +        if (r > 0) {
> > +            env->tsc_khz = r;
> > +        }
> > +    }
> > +
> >      if (has_xsave) {
> >          env->kvm_xsave_buf = qemu_memalign(4096, sizeof(struct kvm_xsave));
> >      }
> > -- 
> > 2.4.8
> > 
> 
> -- 
> Eduardo