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client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; pr=C Received: from SATLEXMB04.amd.com (165.204.84.17) by SJ1PEPF000026C7.mail.protection.outlook.com (10.167.244.104) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.8922.22 via Frontend Transport; Wed, 16 Jul 2025 06:10:13 +0000 Received: from BLR-L1-NDADHANI (10.180.168.240) by SATLEXMB04.amd.com (10.181.40.145) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.39; Wed, 16 Jul 2025 01:10:04 -0500 From: Nikunj A Dadhania To: Tom Lendacky , Borislav Petkov , Sean Christopherson CC: , , , , , Subject: Re: [PATCH] x86/sev: Improve handling of writes to intercepted GUEST_TSC_FREQ In-Reply-To: References: <20250711041200.87892-1-nikunj@amd.com> <20250714104424.GGaHTfiFxI_pf-vhRn@fat_crate.local> <76e0988d-279f-be58-51d9-621806dbb453@amd.com> <20250714161639.GLaHUtZwleS3COfxxX@fat_crate.local> <20250715083827.GBaHYTg9eU55LcHKR1@fat_crate.local> <85ecuhx1eh.fsf@amd.com> Date: Wed, 16 Jul 2025 06:09:56 +0000 Message-ID: <85bjpkwtsb.fsf@amd.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-ClientProxiedBy: SATLEXMB04.amd.com (10.181.40.145) To SATLEXMB04.amd.com (10.181.40.145) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ1PEPF000026C7:EE_|LV2PR12MB5798:EE_ X-MS-Office365-Filtering-Correlation-Id: 6cd7587e-3ff4-4e25-e729-08ddc42f6dbe X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|82310400026|376014|36860700013|1800799024; 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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 Jul 2025 06:10:13.9437 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 6cd7587e-3ff4-4e25-e729-08ddc42f6dbe 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: SJ1PEPF000026C7.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV2PR12MB5798 Tom Lendacky writes: > On 7/15/25 04:13, Nikunj A Dadhania wrote: >> Borislav Petkov writes: >> >>> On Mon, Jul 14, 2025 at 09:36:04AM -0700, Sean Christopherson wrote: >>>> Or as Tom suggested, return ES_EXCEPTION and let the kernel's normal machinery >>>> WARN on the bad WRMSR. >>> >>> Ack. >> >> That will panic the SNP guest instead of #GP: >> >> root@ubuntu:~# wrmsr 0xc0010134 0 >> [ 20.804335] ------------[ cut here ]------------ >> [ 20.804336] WARNING: arch/x86/coco/sev/vc-handle.c:383 at vc_handle_exitcode.part.0+0xc1b/0x1090, CPU#0: wrmsr/607 >> ... >> [ 20.804507] SEV: Unsupported exception in #VC instruction emulation - can't continue >> [ 20.804508] ------------[ cut here ]------------ >> [ 20.804508] kernel BUG at arch/x86/coco/sev/vc-handle.c:123! >> [ 20.804514] Oops: invalid opcode: 0000 [#1] SMP NOPTI > > Did you fill in the context with the #GP, i.e., ctxt->fi.vector and > ctxt->fi.error_code? Ah OK, I didn't know that; after populating the X86_TRAP_GP, SNP guest does not panic anymore. + if (WARN_ON_ONCE(write)) { + ctxt->fi.vector = X86_TRAP_GP; + ctxt->fi.error_code = 0; + return ES_EXCEPTION; + } $ wrmsr 0xc0010134 100 wrmsr: CPU 0 cannot set MSR 0x00000001 to 0x0000000000000064 $ wrmsr 0x10 100 wrmsr: CPU 0 cannot set MSR 0x00000010 to 0x0000000000000064 I have sent an updated patch. Regards, Nikunj