Re: [Xen-devel] PVH VCPU hotplug support v7?

[Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>]

On 07/31/2017 03:29 PM, Boris Ostrovsky wrote:
> On 07/31/2017 10:12 AM, Andrew Cooper wrote:
> > On 31/07/17 14:55, Boris Ostrovsky wrote:
> > > On 07/31/2017 09:20 AM, Ross Lagerwall wrote:
> > > > Hi Boris,
> > > >
> > > > I've modified your PVH VCPU hotplug support v6 patch series [1] to
> > > > support HVM guests running _with_ a device model for XenServer's
> > > > purposes. This is useful because it moves the vCPU hotplug handling
> > > > out of QEMU and allows it to mostly be shared with PVH. It will also
> > > > allow unplugging vCPUs (libxl currently only does cpu-add for upstream
> > > > qemu).
> > > >
> > > > Are you still planning on continuing with that patch series since your
> > > > commit to Linux [2]?
> > > This series has been put on hold until we figure out what to do with
> > > hotplug for PVH dom0. (The problem was the "dual" view by dom0 of APCI
> > > CPU namespace --- on hotplug event dom0 has to somehow figure out
> > > whether the event was due to (dis)appearance of a physical or virtual CPU).
> > >
> > > I don't think this has been dealt with yet (copying Roger).
> >  From the point of view of unblocking several pieces of work, it would be
> > fine for this logic to be behind an emulation flag, just like LAPIC/etc.
> The (I think) last message discussing this series was
>
> https://lists.xenproject.org/archives/html/xen-devel/2017-01/msg00143.html
>
> Are you suggesting extracting pieces that would move hotplug support for
> HVM guests from qemu to hypervisor/toolstack but leave all PVH-specific
> code out? (The feature flag is part of this series ---
> https://lists.xenproject.org/archives/html/xen-devel/2017-01/msg00059.html)
I think(?) Andrew was suggesting to have an emulation flag such that 
hotplug support is moved into the hypervisor for HVM guests _and_ PVH 
guests except for PVH dom0.
I don't know what work this unblocks that he was referring to.

--
Ross Lagerwall

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