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22 Jun 2022 11:43:06 -0700 X-IronPort-AV: E=Sophos;i="5.92,212,1650956400"; d="scan'208";a="677695719" Received: from bshakya-mobl.amr.corp.intel.com (HELO [10.212.188.76]) ([10.212.188.76]) by fmsmga003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Jun 2022 11:43:05 -0700 Message-ID: <99d72d58-a9bb-d75c-93af-79d497dfe176@intel.com> Date: Wed, 22 Jun 2022 11:42:46 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.1 Subject: Re: [PATCH Part2 v6 05/49] x86/sev: Add RMP entry lookup helpers Content-Language: en-US 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" References: <8f63961f00fd170ba0e561f499292175f3155d26.1655761627.git.ashish.kalra@amd.com> <25be3068-be13-a451-86d4-ff4cc12ddb23@intel.com> <681e4e45-eff1-600c-9b81-1fa9bdf24232@intel.com> From: Dave Hansen In-Reply-To: Content-Type: text/plain; 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b=DENAg/CjeeDLrQ5lRY95Oj56U8KecUXiNn8OLGIXVE12Ih988IZUcVOgSTLb+hNvIywhiw 1wcLazNkoYhv69tbekdHAHwvNwdUwNHQmZPMf+ipspU0xg44YpzSk6/K3vB3q3FnAotupH 9i3fla0eXPEDChKjAnc/KsyZh1wT9M8= X-Rspamd-Queue-Id: A10CE200AD X-Rspam-User: Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=WWhPeS0F; spf=none (imf03.hostedemail.com: domain of dave.hansen@intel.com has no SPF policy when checking 192.55.52.43) smtp.mailfrom=dave.hansen@intel.com; dmarc=pass (policy=none) header.from=intel.com X-Rspamd-Server: rspam08 X-Stat-Signature: ik33kw4ajemgzw5gemwfunqqyyha6qua X-HE-Tag: 1655923407-619040 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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.