Re: [Xen-devel] PVH CPU hotplug design document

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

>> From Linux perspective one option could be to have domU with PV-style
>> vCPU on/offlining based on xenstore and switch to ACPI hotplug if/when
>> it becomes available. This, however, will need an indication from the
>> hypervisor. We could, for example, set ACPI_FADT_HW_REDUCED, as we
>> discussed earlier.
> I think we shouldn't overload that flag. Didn't we settle already on using
> two CPUID flags (of for PV-style onlining/offlining, the other for ACPI
> hot(un)plug)? With that I think I could then be talked into accepting the
> existence of two different models (and kernels could pick which one(s)
> they would like to support).

I forgot about existence of ACPI_FADT_HW_REDUCED until this morning,
which is why I mentioned it now.

We can go with CPUID flags although I am not sure why we'd need two. I'd
think that OS can be expected to always support PV-style so the flag
would indicate support for ACPI-based hotplug.

-boris


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