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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 23.01.17 at 16:43, <boris.ostrovsky@xxxxxxxxxx> wrote:
>>> 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.

Well, to date PV style wasn't meant to be supported, was it? In which
case it would be legitimate to put it behind a feature flag. That would
then also pave a road towards removing the support for this (and
simply no longer setting that flag).

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel