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

[Juergen Gross]

On 10.11.23 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.

I'm in favor of an "official" way to get the domid.

As this might be needed on other architectures, too, I guess this will most
likely require a (stable) hypercall.

As soon as this is available, I'd be happy to change Mini-OS again to use the
new hypercall. In order not to block my Xenstore-stubdom series, I'd like to
use the hack of this patch until then. Maybe I should rename the function to
get_own_domid() in order to avoid having to change the user(s).


Juergen

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