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David Alan Gilbert" , , , , Brijesh Singh Subject: [PATCH v6 08/42] x86/sev-es: initialize sev_status/features within #VC handler Date: Fri, 8 Oct 2021 13:04:19 -0500 Message-ID: <20211008180453.462291-9-brijesh.singh@amd.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20211008180453.462291-1-brijesh.singh@amd.com> References: <20211008180453.462291-1-brijesh.singh@amd.com> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.180.168.240] X-ClientProxiedBy: SATLEXMB03.amd.com (10.181.40.144) To SATLEXMB04.amd.com (10.181.40.145) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 27db9027-eae2-420a-048a-08d98a863615 X-MS-TrafficTypeDiagnostic: SN6PR12MB2816: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:8882; X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:SATLEXMB04.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(4636009)(36840700001)(46966006)(186003)(110136005)(54906003)(2906002)(26005)(8936002)(7696005)(8676002)(44832011)(70586007)(316002)(426003)(5660300002)(4326008)(16526019)(7406005)(336012)(83380400001)(82310400003)(81166007)(2616005)(47076005)(36860700001)(70206006)(508600001)(1076003)(86362001)(356005)(36756003)(6666004)(7416002)(2101003)(36900700001);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Oct 2021 18:05:28.5594 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 27db9027-eae2-420a-048a-08d98a863615 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: CO1NAM11FT048.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN6PR12MB2816 From: Michael Roth Generally access to MSR_AMD64_SEV is only safe if the 0x8000001F CPUID leaf indicates SEV support. With SEV-SNP, CPUID responses from the hypervisor are not considered trustworthy, particularly for 0x8000001F. SEV-SNP provides a firmware-validated CPUID table to use as an alternative, but prior to checking MSR_AMD64_SEV there are no guarantees that this is even an SEV-SNP guest. Rather than relying on these CPUID values early on, allow SEV-ES and SEV-SNP guests to instead use a cpuid instruction to trigger a #VC and have it cache MSR_AMD64_SEV in sev_status, since it is known to be safe to access MSR_AMD64_SEV if a #VC has triggered. Signed-off-by: Michael Roth Signed-off-by: Brijesh Singh --- arch/x86/kernel/sev-shared.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c index 8ee27d07c1cd..2796c524d174 100644 --- a/arch/x86/kernel/sev-shared.c +++ b/arch/x86/kernel/sev-shared.c @@ -191,6 +191,20 @@ void __init do_vc_no_ghcb(struct pt_regs *regs, unsigned long exit_code) if (exit_code != SVM_EXIT_CPUID) goto fail; + /* + * A #VC implies that either SEV-ES or SEV-SNP are enabled, so the SEV + * MSR is also available. Go ahead and initialize sev_status here to + * allow SEV features to be checked without relying solely on the SEV + * cpuid bit to indicate whether it is safe to do so. + */ + if (!sev_status) { + unsigned long lo, hi; + + asm volatile("rdmsr" : "=a" (lo), "=d" (hi) + : "c" (MSR_AMD64_SEV)); + sev_status = (hi << 32) | lo; + } + sev_es_wr_ghcb_msr(GHCB_CPUID_REQ(fn, GHCB_CPUID_REQ_EAX)); VMGEXIT(); val = sev_es_rd_ghcb_msr(); -- 2.25.1