Re: [Xen-devel] [PATCH v3 15/28] x86/cpu: Sysctl and common infrastructure for levelling context switching

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 15/03/16 17:35, Joao Martins wrote:
>
> On 03/15/2016 03:35 PM, Andrew Cooper wrote:
>> A toolstack needs to know how much control Xen has over the visible cpuid
>> values in PV guests.  Provide an explicit mechanism to query what Xen is
>> capable of.
>>
>> This interface will currently report no capabilities.  This change is
>> scaffolding for future patches, which will introduce detection and switching
>> logic, after which the interface will report hardware capabilities correctly.
>>
>> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>> ---
>> CC: Jan Beulich <JBeulich@xxxxxxxx>
>>
>> v3:
>>  * Reintroduce XEN_SYSCTL_get_levelling_caps (requested by Joao for some
>>    libvirt development he has planned).
> Hey Andrew,
>
> Perhaps we got mixed in between threads but just to clarify: the exposure of
> XEN_SYSCTL_get_levelling_caps isn't related to libvirt but rather related to
> libxc cpuid policy[0] for supporting CPU topology on PV guests in the purpose 
> of
> the series I proposed here[1]. The libvirt related one was about the exposure 
> of
> featuresets (Patch 21) and/or stabilization of hw_caps format (Patch 2). My
> apologies, if there was something I said that lead you into error.
>
> Joao
>
> [0] http://lists.xenproject.org/archives/html/xen-devel/2016-03/msg00397.html
> [1] http://lists.xenproject.org/archives/html/xen-devel/2016-02/msg03115.html

Sorry - my mistake.  Either way, you still need this hypercall and
hopefully it is in a suitable form for you to use.

~Andrew

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