Re: [Xen-devel] [PATCH 04/13] x86/hvm: Setup TSC scaling ratio

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 23.10.15 at 10:18, <haozhong.zhang@xxxxxxxxx> wrote:
> On Fri, Oct 23, 2015 at 01:59:46AM -0600, Jan Beulich wrote:
>> >>> On 23.10.15 at 09:44, <haozhong.zhang@xxxxxxxxx> wrote:
>> > On Thu, Oct 22, 2015 at 07:13:07AM -0600, Jan Beulich wrote:
>> >> >>> On 28.09.15 at 09:13, <haozhong.zhang@xxxxxxxxx> wrote:
>> 
>> Please remember to trim your replies.
>> 
>> >> > @@ -2023,6 +2051,9 @@ static int hvm_load_cpu_ctxt(struct domain *d, 
> hvm_domain_context_t *h)
>> >> >      if ( hvm_funcs.load_cpu_ctxt(v, &ctxt) < 0 )
>> >> >          return -EINVAL;
>> >> >  
>> >> > +    if ( !v->domain->arch.vtsc && hvm_funcs.tsc_scaling_supported )
>> >> > +        hvm_setup_tsc_scaling(v);
>> >> 
>> >> What's the rationale for putting it in this function?
>> > 
>> > hvm_load_cpu_ctxt() is called in the migration to restore vcpu's state
>> > including TSC related things, so hvm_setup_tsc_scaling() is called
>> > here.
>> > 
>> > hvm_vcpu_reset_state() is not called in the migration, so we cannot
>> > rely on the call to hvm_setup_tsc_scaling() there.
>> 
>> All that is understood, but doesn't explain why the scaling setup gets
>> done here instead of somewhere after _all_ state got loaded.
> 
> Because vcpu is waken up at the end of hvm_vcpu_reset_state(), the
> setup of TSC scaling should be done before that.

But we're talking about hvm_load_cpu_ctxt() here.

Jan


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