Re: [Xen-devel] [PATCH v3 12/13] vmx: Add VMX RDTSC(P) scaling support

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 14.01.16 at 05:52, <haozhong.zhang@xxxxxxxxx> wrote:
> On 01/12/16 09:48, Jan Beulich wrote:
>> >>> On 31.12.15 at 04:03, <haozhong.zhang@xxxxxxxxx> wrote:
>> > @@ -2003,6 +2011,10 @@ static struct hvm_function_table __initdata 
> vmx_function_table = {
>> >      .altp2m_vcpu_update_vmfunc_ve = vmx_vcpu_update_vmfunc_ve,
>> >      .altp2m_vcpu_emulate_ve = vmx_vcpu_emulate_ve,
>> >      .altp2m_vcpu_emulate_vmfunc = vmx_vcpu_emulate_vmfunc,
>> > +    .default_tsc_scaling_ratio   = VMX_TSC_MULTIPLIER_DEFAULT,
>> > +    .max_tsc_scaling_ratio       = VMX_TSC_MULTIPLIER_MAX,
>> > +    .tsc_scaling_ratio_frac_bits = 48,
>> > +    .setup_tsc_scaling           = vmx_setup_tsc_scaling,
>> >  };
>> >  
>> >  /* Handle VT-d posted-interrupt when VCPU is running. */
>> > @@ -2107,6 +2119,9 @@ const struct hvm_function_table * __init 
>> > start_vmx(void)
>> >           && cpu_has_vmx_secondary_exec_control )
>> >          vmx_function_table.pvh_supported = 1;
>> >  
>> > +    if ( cpu_has_vmx_tsc_scaling )
>> > +        vmx_function_table.tsc_scaling_supported = 1;
>> 
>> Do you actually still need this separate flag field? I.e. can't you
>> derive this from one of the other four fields?
> 
> Yes, unless other four fields are set conditionally instead of being
> hardcoded in hvm_funcs.

Indeed I'd expect (at least one of) them to be set (or zapped)
conditionally, just like is being done for some other ones.

Jan


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