linux-kernel - Re: [PATCH v3 09/22] KVM: Do processor compatibility check on resume

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Date:   Mon, 5 Sep 2022 17:27:12 +0800
From:   Yuan Yao <yuan.yao@...ux.intel.com>
To:     isaku.yamahata@...el.com
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>, Will Deacon <will@...nel.org>,
        isaku.yamahata@...il.com, Kai Huang <kai.huang@...el.com>,
        Chao Gao <chao.gao@...el.com>,
        Atish Patra <atishp@...shpatra.org>,
        Shaokun Zhang <zhangshaokun@...ilicon.com>,
        Qi Liu <liuqi115@...wei.com>,
        John Garry <john.garry@...wei.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Huang Ying <ying.huang@...el.com>,
        Huacai Chen <chenhuacai@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH v3 09/22] KVM: Do processor compatibility check on resume

On Mon, Sep 05, 2022 at 04:40:14PM +0800, Yuan Yao wrote:
> On Thu, Sep 01, 2022 at 07:17:44PM -0700, isaku.yamahata@...el.com wrote:
> > From: Isaku Yamahata <isaku.yamahata@...el.com>
> >
> > So far the processor compatibility check is not done on resume. It should
> > be done.
>
> The resume happens for resuming from S3/S4, so the compatibility
> checking is used to detecte CPU replacement, or resume from S4 on an
> different machine ?

By did experiments, I found the resume is called once on CPU 0 before
other CPUs come UP, so yes it's necessary to check it.

>
> >
> > Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> > ---
> >  virt/kvm/kvm_main.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> >
> > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> > index 0ac00c711384..fc55447c4dba 100644
> > --- a/virt/kvm/kvm_main.c
> > +++ b/virt/kvm/kvm_main.c
> > @@ -5715,6 +5715,13 @@ static int kvm_suspend(void)
> >
> >  static void kvm_resume(void)
> >  {
> > +	if (kvm_arch_check_processor_compat())
> > +		/*
> > +		 * No warning here because kvm_arch_check_processor_compat()
> > +		 * would have warned with more information.
> > +		 */
> > +		return; /* FIXME: disable KVM */
> > +
> >  	if (kvm_usage_count) {
> >  		lockdep_assert_not_held(&kvm_count_lock);
> >  		hardware_enable_nolock((void *)__func__);
> > --
> > 2.25.1
> >