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

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Message-ID: <99d72d58-a9bb-d75c-93af-79d497dfe176@intel.com>
Date:   Wed, 22 Jun 2022 11:42:46 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Kalra, Ashish" <Ashish.Kalra@....com>,
        "x86@...nel.org" <x86@...nel.org>,
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Subject: Re: [PATCH Part2 v6 05/49] x86/sev: Add RMP entry lookup helpers

On 6/22/22 11:34, Kalra, Ashish wrote:
>> So, if the RMP entry format changes in future processors, how do we
>> make sure that the kernel does not try to use *this* code on those
>> processors?
> Functions snp_lookup_rmpentry() and dump_rmpentry() which rely on
> this structure definition will need to handle it accordingly.

In other words, old kernels will break on new hardware?

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.