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Re: [PATCH v2 2/5] Mini-OS: get own domid

On 13/11/2023 07:37, Jan Beulich wrote:
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

- 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

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

Couldn't we retroactively generalize the type-agnostic parts of that

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.

For Arm, I can't really think of anything other than hvc/smc which are used for calls to the hypervisor/monitor (so basically hypercalls).

Please suggest if you have a better idea.


Julien Grall



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