Re: [RFC 03/38] x86/hyperlaunch: convert max vcpu determination to domain builder

[Alejandro Vallejo <agarciav@amd.com>]

On Tue Apr 22, 2025 at 9:36 PM BST, Jason Andryuk wrote:
> On 2025-04-19 18:07, Daniel P. Smith wrote:
>> +        limit = dom0_max_vcpus();
>
> dom0_max_vcpus() applies Xen's dom0_max_vcpus command line option.  That 
> is desirable for a traditional dom0.  For a disaggregated, Hyperlaunch 
> system, I'm not sure it's appropriate.  Considering there can multiple 
> control domains, it's more questionable.
>
> Might it be better to only apply Xen "dom0" command line options to 
> non-hyperlaunch dom0?  Or a domain with all of 
> BUILD_CAPS_CONTROL/HARDWARE/XENSTORE?

Alternatively, why not apply it to the hardware domain instead? That's
guaranteed to be (at most) one, and will still function appropriately
when doing non-DTB based boots.

I'll make this adjustment while rebasing this rfc against my latest
hlaunch series.

>
> I guess it could stay as-is, but it seems unusual.

And would probably be particularly weird when it applies to all your
control domains and _not to your hardware domain, which incidentally is
the one domain with domid 0.

>
> Regards,
> Jason

Cheers,
Alejandro