Subject: Re: [PATCH v3 6/9] x86/smpboot: Support parallel startup of secondary
 CPUs
To:     David Woodhouse <dwmw2@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>
Cc:     Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "x86@kernel.org" <x86@kernel.org>,
        "H . Peter Anvin" <hpa@zytor.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        "Paul E . McKenney" <paulmck@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "rcu@vger.kernel.org" <rcu@vger.kernel.org>,
        "mimoja@mimoja.de" <mimoja@mimoja.de>,
        "hewenliang4@huawei.com" <hewenliang4@huawei.com>,
        "hushiyuan@huawei.com" <hushiyuan@huawei.com>,
        "luolongjun@huawei.com" <luolongjun@huawei.com>,
        "hejingxian@huawei.com" <hejingxian@huawei.com>,
        Joerg Roedel <joro@8bytes.org>
References: <20211215145633.5238-1-dwmw2@infradead.org>
 <20211215145633.5238-7-dwmw2@infradead.org>
 <d10f529e-b1ee-6220-c6fc-80435f0061ee@amd.com>
 <f25c6ad00689fee6ce3e294393c13f3dcdd5985f.camel@infradead.org>
From:   Tom Lendacky <thomas.lendacky@amd.com>
Message-ID: <3d8e2d0d-1830-48fb-bc2d-995099f39ef0@amd.com>
Date:   Thu, 16 Dec 2021 13:00:11 -0600
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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

>