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client-ip=165.204.84.17; helo=satlexmb07.amd.com; pr=C Received: from satlexmb07.amd.com (165.204.84.17) by BN3PEPF0000B371.mail.protection.outlook.com (10.167.243.168) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.382.0 via Frontend Transport; Sat, 29 Aug 2026 03:40:13 +0000 Received: from purico-9dcchost.amd.com (10.180.168.240) by satlexmb07.amd.com (10.181.42.216) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.45; Fri, 28 Aug 2026 22:40:13 -0500 From: Melody Wang To: CC: LKML , Tom Lendacky , Melody Wang Subject: [PATCH v1 1/8] x86/sev: Make SVSM calls preemption-safe Date: Sat, 29 Aug 2026 03:39:39 +0000 Message-ID: <8e6e89b87e34a8eb2a20d52b0d92c26e7a61ac42.1787973545.git.huibo.wang@amd.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: satlexmb07.amd.com (10.181.42.216) To satlexmb07.amd.com (10.181.42.216) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN3PEPF0000B371:EE_|PH0PR12MB7885:EE_ X-MS-Office365-Filtering-Correlation-Id: c5dc0293-9d30-4dca-eabf-08df057f3c16 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|36860700016|23010399003|376014|82310400026|10067099003|6133799003|3023799007|18002099003|22082099003|11063799006|56012099006; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: 9mqoecRRxa1CTA0kVnozeJ7CYag8a4I9nYCYZJ500Dwm//RkT99HkWJmpFJmNwTqEmkPCvZTKqUCkv8A39Yv/cEWInCOwrTY4SpmBerA+Ukfsa5dvYHKkwuaD1+hnNOlAFq69GvChZIgYarYUunFPOuXHWBoHAHaqi/FxOfRwJpM0nq4W2SFshe7V5qd/nWs5CkQKXH5v4/YI8VBpK8BVNHC3J4W4LJUJBHa5qkRzRO+UH4ENOJ8vrVIHxPW6FJATF7RQ9pdlLj/tOLYIyNj0pjLHkqXIkr/zt9uXNA/tTkIqlfnej/YkwDqWdR10EATOqIjWuCuFwmEXIEMWdTQLqJKRrL1kUP1e5zd/FGA68KjCWZ1HrAVBm5ThNKKXFijeFYIxEhby2emkXV35Z8qzj/6/O86/SVRCkGrbk2IxcgPo1w8eB+mX5yjyNwKDTjz X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 29 Aug 2026 03:40:13.6601 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: c5dc0293-9d30-4dca-eabf-08df057f3c16 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=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: BN3PEPF0000B371.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH0PR12MB7885 Two functions in the the SVSM vTPM guest implementation do not disable preemption when fetching CAA. The SVSM calling area is a per-CPU structure. When a thread is preempted and migrated to a different CPU after fetching the per-CPU Calling Area Address (CAA), the SVSM call will execute on the new CPU with the original CPU's CAA. Which is wrong. Move the CAA fetching operation inside svsm_perform_call_protocol() which disables interrupts around the SVSM call and thus runs preemption-safe. Signed-off-by: Melody Wang --- arch/x86/coco/sev/svsm.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/arch/x86/coco/sev/svsm.c b/arch/x86/coco/sev/svsm.c index 916d62cd17dc..92ea93f506c0 100644 --- a/arch/x86/coco/sev/svsm.c +++ b/arch/x86/coco/sev/svsm.c @@ -74,6 +74,15 @@ int svsm_perform_call_protocol(struct svsm_call *call) flags = native_local_irq_save(); + /* + * 'caa' is a per-CPU variable. To avoid using a stale or incorrect + * 'caa' if the task is preempted or migrates to another CPU after it + * is fetched, always fetch 'caa' and then issue the SVSM call with + * interrupts disabled. This ensures the correct 'caa' is used even + * under preemption or CPU migration. + */ + call->caa = svsm_get_caa(); + ghcb = __sev_get_ghcb(&state); do { @@ -321,7 +330,6 @@ int snp_svsm_vtpm_send_command(u8 *buffer) { struct svsm_call call = {}; - call.caa = svsm_get_caa(); call.rax = SVSM_VTPM_CALL(SVSM_VTPM_CMD); call.rcx = __pa(buffer); @@ -345,7 +353,6 @@ bool snp_svsm_vtpm_probe(void) if (!snp_vmpl) return false; - call.caa = svsm_get_caa(); call.rax = SVSM_VTPM_CALL(SVSM_VTPM_QUERY); if (svsm_perform_call_protocol(&call)) -- 2.43.0