Re: [Xen-devel] [PATCH 11/13] vmx: Use scaled host TSC to calculate TSC offset

[Haozhong Zhang <haozhong.zhang@xxxxxxxxx>]

On Tue, Oct 27, 2015 at 07:29:44AM -0600, Jan Beulich wrote:
> >>> On 28.09.15 at 09:13, <haozhong.zhang@xxxxxxxxx> wrote:
> > --- a/xen/arch/x86/hvm/vmx/vmx.c
> > +++ b/xen/arch/x86/hvm/vmx/vmx.c
> > @@ -1102,11 +1102,26 @@ static void vmx_handle_cd(struct vcpu *v, unsigned 
> > long value)
> >  
> >  static void vmx_set_tsc_offset(struct vcpu *v, u64 offset, u64 at_tsc)
> >  {
> > +    uint64_t host_tsc, guest_tsc;
> > +    struct domain *d = v->domain;
> > +
> > +    guest_tsc = hvm_get_guest_tsc_fixed(v, at_tsc);
> > +
> > +    if ( cpu_has_vmx_tsc_scaling && !d->arch.vtsc )
> > +    {
> > +        host_tsc = at_tsc ? at_tsc : rdtsc();
> > +        offset = guest_tsc - hvm_scale_tsc(v, host_tsc);
> > +    }
> 
> Considering up to here this is basically the same as SVM's, this
> should imo be factored out into a new hvm_set_tsc_offset(),
> with the caller of hvm_funcs.set_tsc_offset() - lacking a proper
> wrapper anyway - being converted to call that function.
>
I'll add a new hvm_set_tsc_offset() and move the scaling logic from
set_tsc_offset callbacks to it.

> >      vmx_vmcs_enter(v);
> >  
> > +    if ( !nestedhvm_enabled(d) )
> > +        goto out;
> > +
> >      if ( nestedhvm_vcpu_in_guestmode(v) )
> >          offset += nvmx_get_tsc_offset(v);
> >  
> > +out:
> 
> Instead of using goto and a malformed (coding style wise) label,
> please simply extend the if() accordingly.
>
I'll refactor this piece of code to eliminate goto.

Haozhong

> Jan
> 

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