On 08/01/2021 08:38, Paul Durrant wrote: >> -----Original Message----- >> From: Igor Druzhinin <igor.druzhi...@citrix.com> >> Sent: 08 January 2021 00:47 >> To: xen-devel@lists.xenproject.org >> Cc: p...@xen.org; w...@xen.org; i...@xenproject.org; >> anthony.per...@citrix.com; >> andrew.coop...@citrix.com; george.dun...@citrix.com; jbeul...@suse.com; >> jul...@xen.org; >> sstabell...@kernel.org; roger....@citrix.com; Igor Druzhinin >> <igor.druzhi...@citrix.com> >> Subject: [PATCH 2/2] viridian: allow vCPU hotplug for Windows VMs >> >> If Viridian extensions are enabled, Windows wouldn't currently allow >> a hotplugged vCPU to be brought up dynamically. We need to expose a special >> bit to let the guest know we allow it. It appears we can just start exposing >> it without worrying too much about compatibility - see relevant QEMU >> discussion here: >> >> https://patchwork.kernel.org/project/qemu-devel/patch/1455364815-19586-1-git-send-email- >> d...@openvz.org/ > > I don't think that discussion really confirmed it was safe... just that > empirically it appeared to be so. I think we should err on > the side of caution and have this behind a feature flag (but I'm happy for it > to default to on).
QEMU was having this code since 2016 and nobody complained is good enough for me - but if you insist we need an option - ok, I will add one. Igor
