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Re: [PATCH v2 2/5] Mini-OS: get own domid
- To: Julien Grall <julien@xxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 13 Nov 2023 08:37:55 +0100
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- Cc: minios-devel@xxxxxxxxxxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx, samuel.thibault@xxxxxxxxxxxx, wl@xxxxxxx, Juergen Gross <jgross@xxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Delivery-date: Mon, 13 Nov 2023 07:38:02 +0000
- List-id: Mini-os development list <minios-devel.lists.xenproject.org>
On 10.11.2023 18:38, Julien Grall wrote:
> Hi Jan,
>
> On 10/11/2023 12:44, Jan Beulich wrote:
>> On 10.11.2023 13:23, Roger Pau Monné wrote:
>>> On Fri, Nov 10, 2023 at 12:34:32PM +0100, Juergen Gross wrote:
>>>> Get the own domid via creation of a temporary event channel. There is
>>>> no "official" way to read the own domid in PV guests, so use the event
>>>> channel interface to get it:
>>>>
>>>> - allocate an unbound event channel specifying DOMID_SELF for the
>>>> other end
>>>>
>>>> - read the event channel status which will contain the own domid in
>>>> unbound.dom
>>>>
>>>> - close the event channel
>>>
>>> Should we look into introducing a way to expose the domid, so that in
>>> the future we might not need to resort to this workarounds to get the
>>> domid?
>>>
>>> Maybe in the PV-specific cpuid leaf? It's a shame we didn't put it in
>>> a non-HVM specific leaf when it was made available to HVM for pvshim
>>> reasons.
>>
>> Couldn't we retroactively generalize the type-agnostic parts of that
>> leaf?
>
> This would only work for x86. I think we want to have a generic
> hypercalls so it can be used by all arch.
Hmm, yes, perhaps. Otoh it would seem desirable to me if arch-es also
provided some extension to an arch-natural way of feature detection
(which CPUID is on x86), without the need to invoke any hypercalls.
Jan
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