linux-kernel - Re: [PATCH 00/44] KVM: Rework kvm

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Message-ID: <20221108054354.GA1708572@ls.amr.corp.intel.com>
Date:   Mon, 7 Nov 2022 21:43:54 -0800
From:   Isaku Yamahata <isaku.yamahata@...il.com>
To:     "Huang, Kai" <kai.huang@...el.com>
Cc:     "Christopherson,, Sean" <seanjc@...gle.com>,
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Subject: Re: [PATCH 00/44] KVM: Rework kvm_init() and hardware enabling

On Tue, Nov 08, 2022 at 01:09:27AM +0000,
"Huang, Kai" <kai.huang@...el.com> wrote:

> On Mon, 2022-11-07 at 13:46 -0800, Isaku Yamahata wrote:
> > > On Fri, Nov 04, 2022, Isaku Yamahata wrote:
> > > > Thanks for the patch series. I the rebased TDX KVM patch series and it
> > > > worked.
> > > > Since cpu offline needs to be rejected in some cases(To keep at least one
> > > > cpu
> > > > on a package), arch hook for cpu offline is needed.
> > > 
> > > I hate to bring this up because I doubt there's a real use case for SUSPEND
> > > with
> > > TDX, but the CPU offline path isn't just for true offlining of CPUs.  When
> > > the
> > > system enters SUSPEND, only the initiating CPU goes through
> > > kvm_suspend()+kvm_resume(),
> > > all responding CPUs go through CPU offline+online.  I.e. disallowing all
> > > CPUs from
> > > going "offline" will prevent suspending the system.
> > 
> > The current TDX KVM implementation disallows CPU package from offline only
> > when
> > TDs are running.  If no TD is running, CPU offline is allowed.  So before
> > SUSPEND, TDs need to be killed via systemd or something.  After killing TDs,
> > the
> > system can enter into SUSPEND state.
> 
> This seems not correct.  You need one cpu for each to be online in order to
> create TD as well, as TDH.MNG.KEY.CONFIG needs to be called on all packages,
> correct?

That's correct. In such case, the creation of TD fails.  TD creation checks if
at least one cpu is online on all CPU packages.  If no, error.
-- 
Isaku Yamahata <isaku.yamahata@...il.com>