linux-kernel - Re: [PATCH v4 09/26] KVM: Do processor compatibility check on resume

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Date:   Sat, 10 Sep 2022 10:59:19 -0700
From:   Isaku Yamahata <isaku.yamahata@...il.com>
To:     Chao Gao <chao.gao@...el.com>
Cc:     isaku.yamahata@...el.com, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Marc Zyngier <maz@...nel.org>, Will Deacon <will@...nel.org>,
        Yuan Yao <yuan.yao@...ux.intel.com>, isaku.yamahata@...il.com,
        Kai Huang <kai.huang@...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>
Subject: Re: [PATCH v4 09/26] KVM: Do processor compatibility check on resume

On Fri, Sep 09, 2022 at 10:15:16AM +0800,
Chao Gao <chao.gao@...el.com> wrote:

> On Thu, Sep 08, 2022 at 04:25:25PM -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 is called for resuming from S3/S4.  CPUs can be
> >replaced or the kernel can resume from S4 on a different machine.  So
> 
> Are they valid cases handled by other kernel components? Trying to
> handle them in KVM only doesn't help as kernel is likely to fail
> somewhere else.

I guess no.  Actually without the compatibility check, kvm_resume() tries to
enable it by calling hardware_enable_nolock().  The real effect on error case of
this patch is to print out (potentially) more helpful message gracefully by
check_processor_compatibility instead of error message of haredware_enable.
-- 
Isaku Yamahata <isaku.yamahata@...il.com>