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

Kalra, Ashish
2022-06-22T19:43:34Z

[AMD Official Use Only - General]

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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.

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.

Thanks,
Ashish