Re: [PATCH v5 1/6] x86/hvm: Collect information of TSC scaling ratio

[Haozhong Zhang <haozhong.zhang@intel.com>]

On 02/24/16 07:36, Jan Beulich wrote:
> >>> On 23.02.16 at 03:04, <haozhong.zhang@intel.com> wrote:
> > Both VMX TSC scaling and SVM TSC ratio use the 64-bit TSC scaling ratio,
> > but the number of fractional bits of the ratio is different between VMX
> > and SVM. This patch adds the architecture code to collect the number of
> > fractional bits and other related information into fields of struct
> > hvm_function_table so that they can be used in the common code.
> > 
> > Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
> 
> Reviewed-by: Jan Beulich <jbeulich@suse.com>
> 
> albeit I would have wished ...
> 
> > @@ -312,8 +311,8 @@ void hvm_set_guest_tsc_fixed(struct vcpu *v, u64 guest_tsc, u64 at_tsc)
> >      else
> >      {
> >          tsc = at_tsc ?: rdtsc();
> > -        if ( cpu_has_tsc_ratio )
> > -            tsc = hvm_funcs.scale_tsc(v, tsc);
> > +        if ( hvm_tsc_scaling_supported )
> > +            tsc = hvm_funcs.tsc_scaling.scale_tsc(v, tsc);
> 
> ... for these to get their redundancy reduced, .e.g
> 
>             tsc = hvm_funcs.tsc_scaling.scale(v, tsc);
> 
> The R-b may be retained if you elect to make that adjustment.
>

The callback scale_tsc() is later dropped in patch 3. If a new
version of this patch series is needed, I'll make the adjustment
then. Otherwise, I would like to leave it as is.

Thanks,
Haozhong