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From:   Thomas Gleixner <tglx@linutronix.de>
To:     "Kirill A. Shutemov" <kirill@shutemov.name>,
        Tom Lendacky <thomas.lendacky@amd.com>
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Subject: Re: [patch] x86/smpboot: Disable parallel bootup if cc_vendor != NONE
In-Reply-To: <20230530122951.2wu5rwcu26ofov6f@box.shutemov.name>
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Date:   Tue, 30 May 2023 18:00:46 +0200
Message-ID: <87wn0pizbl.ffs@tglx>
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On Tue, May 30 2023 at 15:29, Kirill A. Shutemov wrote:
> On Tue, May 30, 2023 at 02:09:17PM +0200, Thomas Gleixner wrote:
>> The decision to allow parallel bringup of secondary CPUs checks
>> CC_ATTR_GUEST_STATE_ENCRYPT to detect encrypted guests. Those cannot use
>> parallel bootup because accessing the local APIC is intercepted and raises
>> a #VC or #VE, which cannot be handled at that point.
>> 
>> The check works correctly, but only for AMD encrypted guests. TDX does not
>> set that flag.
>> 
>> Check for cc_vendor != CC_VENDOR_NONE instead. That might be overbroad, but
>> definitely works for both AMD and Intel.
>
> It boots fine with TDX, but I think it is wrong. cc_get_vendor() will
> report CC_VENDOR_AMD even on bare metal if SME is enabled. I don't think
> we want it.

Right. Did not think about that.

But the same way is CC_ATTR_GUEST_MEM_ENCRYPT overbroad for AMD. Only
SEV-ES traps RDMSR if I'm understandig that maze correctly.

Thanks,

        tglx