linux-kernel - Re: [PATCH 38/44] KVM: Disable CPU hotplug during hardware enabling

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Message-ID: <d1d4f912292fbfb4f7d88940f22eb9fbcc582ba1.camel@intel.com>
Date:   Thu, 10 Nov 2022 02:20:57 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
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Subject: Re: [PATCH 38/44] KVM: Disable CPU hotplug during hardware enabling

On Thu, 2022-11-10 at 01:08 +0000, Huang, Kai wrote:
> > -	WARN_ON(!irqs_disabled());
> > +	/*
> > +	 * Compatibility checks are done when loading KVM and when enabling
> > +	 * hardware, e.g. during CPU hotplug, to ensure all online CPUs are
> > +	 * compatible, i.e. KVM should never perform a compatibility check
> > on
> > +	 * an offline CPU.
> > +	 */
> > +	WARN_ON(!irqs_disabled() && cpu_active(cpu));
> 
> Comment doesn't match with the code?
> 
> "KVM should never perform a compatibility check on on offline CPU" should be
> something like:
> 
> 	WARN_ON(!cpu_online(cpu));
> 
> So, should the comment be something like below?
> 
> "KVM compatibility check happens before CPU is marked as active".

Also ignore this one as I only thought about hotplug case.