Re: [Xen-devel] [PATCH v10 06/25] x86: refactor psr: L3 CAT: implement Domain init/free and schedule flows.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 06.04.17 at 08:01, <yi.y.sun@xxxxxxxxxxxxxxx> wrote:
> On 17-04-05 09:23:50, Jan Beulich wrote:
>> >>> On 01.04.17 at 15:53, <yi.y.sun@xxxxxxxxxxxxxxx> wrote:
>> > @@ -397,6 +434,11 @@ void psr_ctxt_switch_to(struct domain *d)
>> >      if ( psr_cmt_enabled() )
>> >          psr_assoc_rmid(&reg, d->arch.psr_rmid);
>> >  
>> > +    if ( psra->cos_mask )
>> > +        psr_assoc_cos(&reg, d->arch.psr_cos_ids ?
>> > +                      
>> > d->arch.psr_cos_ids[cpu_to_socket(smp_processor_id())] :
>> > +                      0, psra->cos_mask);
>> 
>> I may have asked this question before, but if so you can see that
>> the code above continues puzzling me: Under what conditions
>> would psra->cos_mask be non-zero, but d->arch.psr_cos_ids be
>> NULL? And why is zero the right value in that case?
>> 
> 'cos_mask' is initialized in 'psr_assoc_init' during cpu starting. The
> 'psr_cos_ids' is allocated during domain init. Here is soft a protection
> to handle abnormal case. Of course, we can use ASSERT to check it.

Obviously a domain failing initialization won't ever make it here,
so an ASSERT() is the maximum I'd consider reasonable here.
We should try to not go overboard with assertions - I appreciate
useful ones, but there is a line beyond which they end up being
clutter.

Jan


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