linux-kernel - Re: [PATCH 5/6] KVM: x86: Remove WARN_ON in kvm_arch_check_processor

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Message-ID: <YedcjqmGYekhPgec@google.com>
Date:   Wed, 19 Jan 2022 00:34:22 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Chao Gao <chao.gao@...el.com>
Cc:     "Tian, Kevin" <kevin.tian@...el.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/6] KVM: x86: Remove WARN_ON in
 kvm_arch_check_processor_compat

On Mon, Jan 17, 2022, Chao Gao wrote:
> On Mon, Jan 17, 2022 at 09:35:04PM +0800, Chao Gao wrote:
> >OK. How about:
> >
> >	/*
> >	 * Compatibility checks are done when loading KVM or in KVM's CPU
> >	 * hotplug callback. It ensures all online CPUs are compatible before
> >	 * running any vCPUs. For other cases, compatibility checks are
> >	 * unnecessary or even problematic. Try to detect improper usages here.
> >	 */
> >	WARN_ON(!irqs_disabled() && !cpu_active(smp_processor_id()));
> 
> Sorry. It should be:
> 	WARN_ON(!irqs_disabled() && cpu_active(smp_processor_id()));

Nice!  That's exactly what I was hoping we could do.