Re: [Xen-devel] [PATCH v1] x86/msr: add Raw and Host domain policies

[Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>]

On Thu, 2018-02-15 at 06:33 -0700, Jan Beulich wrote:
> > > > On 08.02.18 at 11:23, <sergey.dyasli@xxxxxxxxxx> wrote:
> > 
> > --- a/xen/arch/x86/cpu/common.c
> > +++ b/xen/arch/x86/cpu/common.c
> > @@ -118,9 +118,18 @@ void (* __read_mostly ctxt_switch_masking)(const 
> > struct vcpu *next);
> >  
> >  bool __init probe_cpuid_faulting(void)
> >  {
> > +   struct msr_domain_policy *dp = &raw_msr_domain_policy;
> 
> Unless you foresee the variable to be needed for further things
> here, could this be moved into the more narrow scope it's used in
> please?

Will do in v2.

> >     uint64_t val;
> > +   int rc;
> >  
> > -   if (rdmsr_safe(MSR_INTEL_PLATFORM_INFO, val) ||
> > +   if ((rc = rdmsr_safe(MSR_INTEL_PLATFORM_INFO, val)) == 0)
> > +   {
> > +           dp->plaform_info.available = true;
> > +           if (val & MSR_PLATFORM_INFO_CPUID_FAULTING)
> > +                   dp->plaform_info.cpuid_faulting = true;
> > +   }
> > +
> > +   if (rc ||
> >         !(val & MSR_PLATFORM_INFO_CPUID_FAULTING) ||
> >         rdmsr_safe(MSR_INTEL_MISC_FEATURES_ENABLES,
> >                    this_cpu(msr_misc_features)))
> 
> Below here we have
> 
>               setup_clear_cpu_cap(X86_FEATURE_CPUID_FAULTING);
> 
> Shouldn't this be reflected in the host policy?

I guess the correct thing to do for now for host_msr_domain_policy is:

    dp->plaform_info.cpuid_faulting = cpu_has_cpuid_faulting;
    
Looking at the code, calculate_pv_max_policy() will be simplified with
the above change: pv_max_msr_domain_policy will become a copy of host
policy.

This actually brings a question: what to do about per-pCPU MSRs in the
context of MSR policy?

-- 
Thanks,
Sergey
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