linux-kernel - Re: [PATCH Part2 v6 05/49] x86/sev: Add RMP entry lookup helpers

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Date:   Wed, 22 Jun 2022 12:49:52 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Kalra, Ashish" <Ashish.Kalra@....com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
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Subject: Re: [PATCH Part2 v6 05/49] x86/sev: Add RMP entry lookup helpers

On 6/22/22 12:43, Kalra, Ashish wrote:
>> I think that needs to be fixed.  It should be as simple as a
>> model/family check, though.  If someone (for example) attempts to
>> use SNP (and thus snp_lookup_rmpentry() and dump_rmpentry()) code
>> on a newer CPU, the kernel should refuse.
> More specifically I am thinking of adding RMP entry field accessors
> so that they can do this cpu model/family check and return the
> correct field as per processor architecture.

That will be helpful down the road when there's more than one format.
But, the real issue is that the kernel doesn't *support* a different RMP
format.  So, the SNP support should be disabled when encountering a
model/family other than the known good one.