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

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Date:   Thu, 16 Dec 2021 13:00:11 -0600
From:   Tom Lendacky <thomas.lendacky@....com>
To:     David Woodhouse <dwmw2@...radead.org>,
        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" <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" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "rcu@...r.kernel.org" <rcu@...r.kernel.org>,
        "mimoja@...oja.de" <mimoja@...oja.de>,
        "hewenliang4@...wei.com" <hewenliang4@...wei.com>,
        "hushiyuan@...wei.com" <hushiyuan@...wei.com>,
        "luolongjun@...wei.com" <luolongjun@...wei.com>,
        "hejingxian@...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 12/16/21 12:24 PM, David Woodhouse wrote:
> 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?

Calling cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT) will return true for 
an SEV-ES guest.

Thanks,
Tom

>