Re: [Xen-devel] [PATCH v4 02/12] x86: improve psr scheduling code

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 10/04/15 08:24, Chao Peng wrote:
> On Thu, Apr 09, 2015 at 10:01:53PM +0100, Andrew Cooper wrote:
>> On 09/04/2015 10:18, Chao Peng wrote:
>>> +static inline void psr_assoc_init(unsigned int cpu)
>>> +{
>>> +    struct psr_assoc *psra = &per_cpu(psr_assoc, cpu);
>>> +
>>> +    if ( psr_cmt_enabled() )
>>> +        rdmsrl(MSR_IA32_PSR_ASSOC, psra->val);
>>> +}
>> On further consideration, this would probably be better as a void
>> function which used this_cpu() rather than per_cpu().
>>
>> Absolutely nothing good can come of calling it with cpu !=
>> smp_processor_id(), so we should avoid that situation arising in the
>> first place.
> Agreed.
>
>>> +static void psr_cpu_init(unsigned int cpu)
>>> +{
>>> +    psr_assoc_init(cpu);
>>> +}
>> This can also turn into a void helper.
> This is, however, a little different. The next patch will add
> cat_cpu_init() which will make use of this 'cpu' parameter. So do you
> mean calling smp_processor_id() in cat_cpu_init() as well?

Yes - that is probably best.  While cat_cpu_init() doesn't actually
interact with any MSRs, we still never want to be in a position to
execute it against the "wrong" cpu.

~Andrew

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