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

[Joao Martins <joao.m.martins@xxxxxxxxxx>]

On 03/15/2016 07:29 PM, Andrew Cooper wrote:
> 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.
OK, Thanks a lot!

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