linux-kernel - Re: [PATCH v3 6/9] x86/smpboot: Support parallel startup of secondary CPUs

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Date:   Thu, 16 Dec 2021 18:24:08 +0000
From:   David Woodhouse <dwmw2@...radead.org>
To:     Tom Lendacky <thomas.lendacky@....com>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H . Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        rcu@...r.kernel.org, mimoja@...oja.de, hewenliang4@...wei.com,
        hushiyuan@...wei.com, luolongjun@...wei.com, hejingxian@...wei.com,
        Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH v3 6/9] x86/smpboot: Support parallel startup of
 secondary CPUs

On Thu, 2021-12-16 at 08:24 -0600, Tom Lendacky wrote:

> This will break an SEV-ES guest because CPUID will generate a #VC and a 
> #VC handler has not been established yet.
> 
> I guess for now, you can probably just not enable parallel startup for 
> SEV-ES guests.

OK, thanks. I'll expand it to allow 24 bits of (physical) APIC ID then,
since it's no longer limited to CPUs without X2APIC. Then we can
refrain from doing parallel bringup for SEV-ES guests, as you suggest.

What precisely is the check I should be using for that?

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