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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2014-03-13 at 15:48 +0000, Jan Beulich wrote:
> >>> 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...

Worthy of a comment at least I think ;-)


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