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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.02.18 at 11:33, <sergey.dyasli@xxxxxxxxxx> wrote:
> On Thu, 2018-02-15 at 06:33 -0700, Jan Beulich wrote:
>> > > > On 08.02.18 at 11:23, <sergey.dyasli@xxxxxxxxxx> wrote:
>> >    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?

How does per-pCPU-ness of an MSR affect the policy? Are you
thinking of CPUs with different capabilities? We assume all CPUs
are identical in many other places.

Jan


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