[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [PATCH 2/2] viridian: allow vCPU hotplug for Windows VMs
> -----Original Message----- > From: Igor Druzhinin <igor.druzhinin@xxxxxxxxxx> > Sent: 08 January 2021 11:30 > To: paul@xxxxxxx; xen-devel@xxxxxxxxxxxxxxxxxxxx > Cc: wl@xxxxxxx; iwj@xxxxxxxxxxxxxx; anthony.perard@xxxxxxxxxx; > andrew.cooper3@xxxxxxxxxx; > george.dunlap@xxxxxxxxxx; jbeulich@xxxxxxxx; julien@xxxxxxx; > sstabellini@xxxxxxxxxx; > roger.pau@xxxxxxxxxx > Subject: Re: [PATCH 2/2] viridian: allow vCPU hotplug for Windows VMs > > On 08/01/2021 08:38, Paul Durrant wrote: > >> -----Original Message----- > >> From: Igor Druzhinin <igor.druzhinin@xxxxxxxxxx> > >> Sent: 08 January 2021 00:47 > >> To: xen-devel@xxxxxxxxxxxxxxxxxxxx > >> Cc: paul@xxxxxxx; wl@xxxxxxx; iwj@xxxxxxxxxxxxxx; > >> anthony.perard@xxxxxxxxxx; > >> andrew.cooper3@xxxxxxxxxx; george.dunlap@xxxxxxxxxx; jbeulich@xxxxxxxx; > >> julien@xxxxxxx; > >> sstabellini@xxxxxxxxxx; roger.pau@xxxxxxxxxx; Igor Druzhinin > >> <igor.druzhinin@xxxxxxxxxx> > >> 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- > >> den@xxxxxxxxxx/ > > > > 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. > Given that it has not yet been in a release, perhaps you could just guard this and the implementation of leaf 0x40000005 using HVMPV_ex_processor_masks? Paul > Igor
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