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Subject: Re: [PATCH v2 03/12] x86/sev: Add an x86 version of prot_guest_has()
To:     Borislav Petkov <bp@alien8.de>
Cc:     linux-kernel@vger.kernel.org, x86@kernel.org,
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References: <cover.1628873970.git.thomas.lendacky@amd.com>
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From:   Tom Lendacky <thomas.lendacky@amd.com>
Message-ID: <f4b8bc3c-5158-cd04-6e12-77f08036ea19@amd.com>
Date:   Tue, 17 Aug 2021 10:22:52 -0500
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On 8/15/21 9:39 AM, Borislav Petkov wrote:
> On Sun, Aug 15, 2021 at 08:53:31AM -0500, Tom Lendacky wrote:
>> It's not a cross-vendor thing as opposed to a KVM or other hypervisor
>> thing where the family doesn't have to be reported as AMD or HYGON.
> 
> What would be the use case? A HV starts a guest which is supposed to be
> encrypted using the AMD's confidential guest technology but the HV tells
> the guest that it is not running on an AMD SVM HV but something else?
> 
> Is that even an actual use case?
> 
> Or am I way off?
> 
> I know we have talked about this in the past but this still sounds
> insane.

Maybe the KVM folks have a better understanding of it...

I can change it to be an AMD/HYGON check...  although, I'll have to check
to see if any (very) early use of the function will work with that.

At a minimum, the check in arch/x86/kernel/head64.c will have to be
changed or removed. I'll take a closer look.

Thanks,
Tom

>