Re: [Xen-devel] [RESEND PATCH v4 09/10] vmx: Add VMX RDTSC(P) scaling support

["Zhang, Haozhong" <haozhong.zhang@xxxxxxxxx>]

On 02/05/16 22:06, Jan Beulich wrote:
> >>> On 19.01.16 at 03:55, <haozhong.zhang@xxxxxxxxx> wrote:
> > @@ -2107,6 +2115,14 @@ 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.default_tsc_scaling_ratio = 
> > VMX_TSC_MULTIPLIER_DEFAULT;
> > +        vmx_function_table.max_tsc_scaling_ratio = VMX_TSC_MULTIPLIER_MAX;
> > +        vmx_function_table.tsc_scaling_ratio_frac_bits = 48;
> > +        vmx_function_table.setup_tsc_scaling = vmx_setup_tsc_scaling;
> > +    }
> 
> Same comments here as on the earlier patch - it indeed looks as if
> tsc_scaling_ratio_frac_bits would be the ideal field to dynamically
> initialize, as it being zero will not yield any bad behavior afaict.
>

Yes, I'll make changes similar to my reply under patch 4.

> Also please consider making all fields together a sub-structure
> of struct hvm_function_table, such that the above would become
> 
>         vmx_function_table.tsc_scaling.default_ratio = 
> VMX_TSC_MULTIPLIER_DEFAULT;
>         vmx_function_table.tsc_scaling.max_ratio = VMX_TSC_MULTIPLIER_MAX;
>         vmx_function_table.tsc_scaling.ratio_frac_bits = 48;
>         vmx_function_table.tsc_scaling.setup = vmx_setup_tsc_scaling;
> 
> keeping everything nicely together.
>

OK, I'll put them in a sub-structure by the earlier patch that
introduces those fields.

> > @@ -258,6 +259,9 @@ extern u64 vmx_ept_vpid_cap;
> >  #define VMX_MISC_CR3_TARGET                     0x01ff0000
> >  #define VMX_MISC_VMWRITE_ALL                    0x20000000
> >  
> > +#define VMX_TSC_MULTIPLIER_DEFAULT              0x0001000000000000ULL
> 
> Considering this and the respective SVM value - do we really
> need the separate field in struct hvm_function_table? Both are
> 1ULL << tsc_scaling.ratio_frac_bits after all.
>

I'll remove VMX_TSC_MULTIPLIER_DEFAULT and DEFAULT_TSC_RATIO (for SVM),
and use ratio_frac_bits to initialize default_ratio.

Thanks,
Haozhong

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