Re: [Xen-devel] [PATCH 2/5] x86: Support enable/disable CDP dynamically and get CDP status

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.09.15 at 13:39, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 02/09/15 09:27, He Chen wrote:
>> +        /* Reset all domain to COS0 */
>> +        for_each_domain( d )
>> +        {
>> +            d->arch.psr_cos_ids[socket] = 0;
>> +            info->cos_to_cbm[0].ref++;
> 
> This is a long running operation and must not be done synchronously like
> this.  Unfortunately, it is not easy to make restartable.
> 
> I think it would be perfectly reasonable to have cdp as a boot time
> switch only, and have no ability to change it at runtime.  I don't see a
> reasonable case to change it dynamically at runtime; users will either
> want to use it, or not.
> 
> Making this a boot-time choice (i.e. psr=cat,cdp) removes all of this
> re-juggling logic, and simplifies things greatly.
> 
> Thoughts?

FWIW I agree.

Jan


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