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To: Dave Hansen , tglx@kernel.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, seanjc@google.com, peterz@infradead.org, thomas.lendacky@amd.com, herbert@gondor.apana.org.au, davem@davemloft.net, ardb@kernel.org Cc: pbonzini@redhat.com, aik@amd.com, Michael.Roth@amd.com, KPrateek.Nayak@amd.com, Tycho.Andersen@amd.com, Nathan.Fontenot@amd.com, jackyli@google.com, pgonda@google.com, rientjes@google.com, jacobhxu@google.com, xin@zytor.com, pawan.kumar.gupta@linux.intel.com, babu.moger@amd.com, dyoung@redhat.com, nikunj@amd.com, john.allen@amd.com, darwi@linutronix.de, linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org, kvm@vger.kernel.org, linux-coco@lists.linux.dev References: <23267200-9fed-43a9-a28b-a6daa701159b@intel.com> Content-Language: en-US From: "Kalra, Ashish" In-Reply-To: <23267200-9fed-43a9-a28b-a6daa701159b@intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ClientProxiedBy: SA1P222CA0086.NAMP222.PROD.OUTLOOK.COM (2603:10b6:806:35e::27) To BL3PR12MB9049.namprd12.prod.outlook.com (2603:10b6:208:3b8::21) Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BL3PR12MB9049:EE_|CH3PR12MB8209:EE_ X-MS-Office365-Filtering-Correlation-Id: 1586dcaf-37b5-4543-d8ad-08de95a58469 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|7416014|376014|921020|56012099003|22082099003|18002099003; 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>> + >> + if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP)) >> + return -EINVAL; >> + >> + if (!(rmp_cfg & MSR_AMD64_SEG_RMP_ENABLED)) >> + return -EINVAL; > > This seems wrong. How about we just make 'X86_FEATURE_RMPOPT' the one > true source of RMP support? > > If you don't have CC_ATTR_HOST_SEV_SNP you: > > setup_clear_cpu_cap(X86_FEATURE_RMPOPT) > > Ditto for MSR_AMD64_SEG_RMP_ENABLED. > > It could also potentially replace the 'rmpopt_wq' checks. > Following up on this ... It is straightforward to clear X86_FEATURE_RMPOPT if the RMPOPT setup function (that is, configure and enable RMPOPT function) gets called, but if CC_ATTR_HOST_SEV_SNP is not set, then __sev_snp_init_locked() (CCP module) does not invoke the RMPOPT setup function. And then as this function snp_perform_rmp_optimization() is an external API, it needs to check for both CC_ATTR_HOST_SEV_SNP and MSR_AMD64_SEG_RMP_ENABLED. Otherwise, we will need to clear X86_FEATURE_RMPOPT, wherever CC_ATTR_HOST_SEV_SNP is cleared all across call sites like the AMD IOMMU driver, AMD SVM-SEV command line parsing support code and AMD CPU detection and BSP init code. And for clearing X86_FEATURE_RMPOPT, if MSR_AMD64_SEG_RMP_ENABLED is not set, the support will need to be added in setup_rmptable(). It is much more straightforward to check for both CC_ATTR_HOST_SEV_SNP and MSR_AMD64_SEG_RMP_ENABLED in this API function itself. Thanks, Ashish