Re: [Qemu-devel] [PATCH 2/3] target-i386: initialize vcpu's TSC rate to the value from KVM

[Haozhong Zhang]

On Mon, Sep 28, 2015 at 01:17:44PM -0300, Eduardo Habkost wrote:
> On Mon, Sep 28, 2015 at 01:38:30PM +0800, Haozhong Zhang wrote:
> > When creating a vcpu, we initialize its TSC rate to the value from
> > KVM (through ioctl KVM_GET_TSC_KHZ).
> > 
> > Signed-off-by: Haozhong Zhang <address@hidden>
> > ---
> >  target-i386/kvm.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> > index 7b0ba17..c2b161a 100644
> > --- a/target-i386/kvm.c
> > +++ b/target-i386/kvm.c
> > @@ -751,6 +751,13 @@ int kvm_arch_init_vcpu(CPUState *cs)
> >          }
> >      }
> >  
> > +    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 = r;
> 
> You are silently overwriting the tsc_khz value set by the user, why?
>

Oh, I need to check if user has provided tsc_khz, and if so then just
use the user-provided value. So I'll replace it with code like

if (env->tsc_khz) {
    kvm_vcpu_ioctl(cs, KVM_SET_TSC_KHZ, env->tsc_khz);
} else {
    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 = r;
}

- Haozhong

> -- 
> Eduardo