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

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Date:   Fri, 22 Jul 2022 13:35:32 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     "Kalra, Ashish" <Ashish.Kalra@....com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Dave Hansen <dave.hansen@...el.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 Thu, Jun 23, 2022 at 10:43:40PM +0000, Kalra, Ashish wrote:
> Yes, that's a nice way to hide it from the rest of the kernel which
> does not require access to this structure anyway, in essence, it
> becomes a private structure.

So this whole discussion whether there should be a model check or not
in case a new RMP format gets added in the future is moot - when a new
model format comes along, *then* the distinction should be done and
added in code - not earlier.

This is nothing else but normal CPU enablement work - it should be done
when it is really needed.

Because the opposite can happen: you can add a model check which
excludes future model X, future model X comes along but does *not*
change the RMP format and then you're going to have to relax that model
check again to fix SNP on the new model X.

So pls add the model checks only when really needed.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette