Re: [Xen-devel] [PATCH RFC v1 40/74] xen/x86: report domain id on cpuid

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 08.01.18 at 11:34, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 08/01/18 10:27, Jan Beulich wrote:
>>>>> On 04.01.18 at 14:05, <wei.liu2@xxxxxxxxxx> wrote:
>>> From: Roger Pau Monne <roger.pau@xxxxxxxxxx>
>>>
>>> Use the ebx register of the hypervisor leaf 1. The eax register on
>>> this leaf is already used to report the Xen major and minor versions.
>> The rationale for doing this is missing. Iirc in past discussions the
>> opinion was voiced (more than once, and iirc by Andrew any maybe
>> others) that a domain in general shouldn't be told about its domain
>> ID. Otherwise I also can't see why we don't have a hypercall for
>> this, and e.g. XTF needs to go through hoops to figure it out. Are
>> those arguments (which I don't recall) not applicable anymore?
>>
>> In the Amazon shim patches thread handing out the domain ID by
>> command line option was suggested as an alternative, which then
>> wouldn't affect other (non-shim) domains, or the client of the shim.
> 
> A guests domid is unconditionally always available in xenstore, and is a
> necessary part of any PV communication.
> 
> Like it or not, domid is part of the guests view of the Xen ABI. 
> Therefore, making it easily accessible is the best course of action
> (especially as pv-shim deliberately doesn't interpose on the xenstore ring).

All understood, yet you don't address the question on the
backgrounds of the change of your opinion here. Or am I
misremembering that earlier on you were against exposing
the domain ID?

Jan


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