[AMD Official Use Only - General] [AMD Official Use Only - General] ________________________________ From: Dave Hansen Sent: Wednesday, June 22, 2022 1:43 PM To: Kalra, Ashish ; x86@kernel.org ; linux-kernel@vger.kernel.org ; kvm@vger.kernel.org ; linux-coco@lists.linux.dev ; linux-mm@kvack.org ; linux-crypto@vger.kernel.org Cc: tglx@linutronix.de ; mingo@redhat.com ; jroedel@suse.de ; Lendacky, Thomas ; hpa@zytor.com ; ardb@kernel.org ; pbonzini@redhat.com ; seanjc@google.com ; vkuznets@redhat.com ; jmattson@google.com ; luto@kernel.org ; dave.hansen@linux.intel.com ; slp@redhat.com ; pgonda@google.com ; peterz@infradead.org ; srinivas.pandruvada@linux.intel.com ; rientjes@google.com ; dovmurik@linux.ibm.com ; tobin@ibm.com ; bp@alien8.de ; Roth, Michael ; vbabka@suse.cz ; kirill@shutemov.name ; ak@linux.intel.com ; tony.luck@intel.com ; marcorr@google.com ; sathyanarayanan.kuppuswamy@linux.intel.com ; alpergun@google.com ; dgilbert@redhat.com ; jarkko@kernel.org 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