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

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Message-ID: <SN6PR12MB2767658F1A362C82922FB2DB8E9A9@SN6PR12MB2767.namprd12.prod.outlook.com>
Date:   Mon, 1 Aug 2022 21:50:37 +0000
From:   "Kalra, Ashish" <Ashish.Kalra@....com>
To:     Borislav Petkov <bp@...en8.de>,
        Sean Christopherson <seanjc@...gle.com>
CC:     Dave Hansen <dave.hansen@...el.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

[AMD Official Use Only - General]

>> I disagree.  Running an old kernel on new hardware with a different 
>> RMP layout should refuse to use SNP, not read/write garbage and likely 
>> corrupt the RMP and/or host memory.

>See my example below.

> And IMO, hiding the non-architectural RMP format in SNP-specific code 
> so that we don't have to churn a bunch of call sites that don't _need_ 
> access to the raw RMP format is a good idea regardless of whether we 
> want to be optimistic or pessimistic about future formats.

>I don't think I ever objected to that.

I agree with what Sean is recommending to do. 

As I mentioned earlier, in the long term and with respect to future platforms, we are going to add architectural support
to read RMP table entries, so this structure will exist only for older platform support.

Thanks,
Ashish