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

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

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


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 ---

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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