Re: [Xen-devel] [PATCH 2/3] x86/idle: update to include further package/core residency MSRs

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 13.03.14 at 16:34, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> On Thu, 2014-03-13 at 14:27 +0000, Jan Beulich wrote:
>> >>> On 13.03.14 at 15:11, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
>> > On Wed, 2014-03-05 at 10:37 +0000, Jan Beulich wrote:
>> >> With the number of these growing it becomes increasingly desirable to
>> >> not repeatedly alter the sysctl interface to accommodate them. Replace
>> >> the explicit listing of numbered states by arrays,
>> > 
>> > I don't have much of an opinion on the hypercall interface, so I'm just
>> > taking that as a given and looking at the tools side accordingly.
>> > 
>> >> unused fields of which will remain untouched by the hypercall.
>> > 
>> > Are you supposed to initialise them to some known sentinal or are the
>> > valid entries identified somewhere else (sorry, don't know much about
>> > x86 pm).
>> 
>> The best thing for the caller would be to zero the whole buffer.
>> But other known out of range values (like all ones) would do to.
>> In the end it's up to the caller to pre-fill the array suitably for it
>> to recognize valid fields.
> 
> That makes sense. It look like your xenpm mods doesn't actually do this
> though?

I should be using calloc() there to avoid future questions of this
kind, but in fact it was intentional: The bounce buffers get cleared
upon allocation, and since I made the bounce direction out-only,
the intended effect is what we want. Too subtle/fragile perhaps...

Jan


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