From nobody Sat Sep 13 22:35:38 2025 Received: from NAM04-BN8-obe.outbound.protection.outlook.com (mail-bn8nam04on2065.outbound.protection.outlook.com [40.107.100.65]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 67A4F1DD885; Mon, 6 Jan 2025 12:47:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=40.107.100.65 ARC-Seal: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736167654; cv=fail; b=HqUkohaUQNSHHj/s0Cwk8ftGqrWiiqBxYV+amxlHGygcgUfix9GtWMMSs/B0oQl6F62hyaggV5bp9NunqDQTMapcwvTH3vxO/92S/BlP/AZ39b0QdJ1OYThRBQTKIeNK3zA36y7M7WOYWyN8NCy3icS6l561PZz4nc1PlkuDceQ= ARC-Message-Signature: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736167654; c=relaxed/simple; bh=+Mt4Xo4gq8YF5s5PTqxV7Wv8SJjh8nDI0ios4yKNSgY=; h=From:To:CC:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=M49vI8AsHpFtefhhXoNxATqQtoRphECtTthszmwS30tivdP770k2Zn6Wq+j6M4mkcgg0F0P1A+IX5NdKuYdcQ6wkTa6aOIU6tHb1Ete7mxDrcu4LJiUU6bbbixBxXy72fuNCc6XKpHPE27u/EM894k/dKmgf72zhfyHyjsxM/so= ARC-Authentication-Results: i=2; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amd.com; spf=fail smtp.mailfrom=amd.com; dkim=pass (1024-bit key) header.d=amd.com header.i=@amd.com header.b=1/8GSJUm; arc=fail smtp.client-ip=40.107.100.65 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amd.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=amd.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=amd.com header.i=@amd.com header.b="1/8GSJUm" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=EwUf8VA95M6SrsIUL9sGwrVYzPTwatZK//qA02syxytYsmPIQ+oaJJKpraCx9f8SubDN348nqtA7xe/eKHUQp+458QdX0TEj1bwau3lTPWJ7uholhaBzNLB5LMFsSeNBB93g0FjAa+JQZGYHk/OBdskXBFqKkWO5geWb4HmfmWH4D8Yy5enGyMY20mbW6oyVqbHRBXqljVeeO4NErLOUq/YIXTCf2tviHGXjiPMk/lmRyz4SCp5p7rb78wPTWNVU3fHfWoSY8qibgxY6CrhkuDiJ0Z+QeXMJxldv16t7/td9Aaco1NP5+oelV4H2Ahj7j87CyyjVyLLbNij89CKOqQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=4pqoswnoX0/qe+gUbJAMNlCMH29+ydjopKLUifvQLc8=; b=vg0AP5n22mUrdwYp8W6fFv865SdJbM+QxRxkHPsLvrDdneaIHPnXjXnzDxUVRhBsH+9tzgg+J2sdVkIuWYQQu5EfFgPjjYoq3xlmC+qFybQNhJydy/QZZcfGhmux038fnPr+t0Xl3AXS3qNX+PO31i3FBrdaKbsAMsn/j73WxPHsUaKVM0/Hcff9PFnVD7vYaMSNIdMSIkQr5R9XnEmp9mnvjlC9MMl3VjtNxiG3NmWq52sp274wruBpBZviXu+YDxbVT8BItFrKmcWkbbDErZbhhTvYlj2UfYRHMOlySmTy7rwm7XaPUxrDiJyKl1ZsHSv52GEWi7ziOD/b2V6Q9Q== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass (sender ip is 165.204.84.17) smtp.rcpttodomain=vger.kernel.org smtp.mailfrom=amd.com; dmarc=pass (p=quarantine sp=quarantine pct=100) action=none header.from=amd.com; dkim=none (message not signed); arc=none (0) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amd.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=4pqoswnoX0/qe+gUbJAMNlCMH29+ydjopKLUifvQLc8=; b=1/8GSJUmf9E2e1IdVQ2nClQUk3GrYISeaXTmLwVBrAPpEyeRjTc24jNttV9hDK7uqSZIuKCOP180ITmlupgT4fHdcqSnqJxEduWiNLNNgOdufc2e8Yba6Cw3+H2mYQcv3mTYYNFmv+pLRSZcBIebE0Xo0syE138lLV6leklAtvc= Received: from PH7P221CA0001.NAMP221.PROD.OUTLOOK.COM (2603:10b6:510:32a::7) by PH0PR12MB7837.namprd12.prod.outlook.com (2603:10b6:510:282::13) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.8314.16; Mon, 6 Jan 2025 12:47:22 +0000 Received: from CY4PEPF0000EDD6.namprd03.prod.outlook.com (2603:10b6:510:32a:cafe::3f) by PH7P221CA0001.outlook.office365.com (2603:10b6:510:32a::7) with Microsoft SMTP Server (version=TLS1_3, cipher=TLS_AES_256_GCM_SHA384) id 15.20.8314.17 via Frontend Transport; Mon, 6 Jan 2025 12:47:22 +0000 X-MS-Exchange-Authentication-Results: spf=pass (sender IP is 165.204.84.17) smtp.mailfrom=amd.com; dkim=none (message not signed) header.d=none;dmarc=pass action=none header.from=amd.com; Received-SPF: Pass (protection.outlook.com: domain of amd.com designates 165.204.84.17 as permitted sender) receiver=protection.outlook.com; client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; pr=C Received: from SATLEXMB04.amd.com (165.204.84.17) by CY4PEPF0000EDD6.mail.protection.outlook.com (10.167.241.202) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.20.8335.7 via Frontend Transport; Mon, 6 Jan 2025 12:47:22 +0000 Received: from gomati.amd.com (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; Mon, 6 Jan 2025 06:47:17 -0600 From: Nikunj A Dadhania To: , , , CC: , , , , , , , , Subject: [PATCH v16 06/13] x86/sev: Change TSC MSR behavior for Secure TSC enabled guests Date: Mon, 6 Jan 2025 18:16:26 +0530 Message-ID: <20250106124633.1418972-7-nikunj@amd.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20250106124633.1418972-1-nikunj@amd.com> References: <20250106124633.1418972-1-nikunj@amd.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable 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-TrafficTypeDiagnostic: CY4PEPF0000EDD6:EE_|PH0PR12MB7837:EE_ X-MS-Office365-Filtering-Correlation-Id: 2cc5a2e8-e4fe-4a34-15b4-08dd2e5043d3 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|36860700013|7416014|1800799024|376014|82310400026; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?5142mRJq4/A1mQ45XovChaIg1/kzKoqMPeqTf9ffv5S4cwS4VdZVvIkfmJaO?= =?us-ascii?Q?F+WOYUFXUMM7IKyTxqg51MoS2vEXvforSpGOC2hzy+xGgkKwvqydfv7U+R3g?= =?us-ascii?Q?A5CdYD1+/yaFtN6mMP38d9sFSaxbPh7/u5LjJEtxMfkbIxDknHt4pAtQqL82?= =?us-ascii?Q?7MZQ71PlUA8U7C0w0TeqHF6dSIZugM8SPdZsQ6h/OXPuApZfzgHuS5c2neYX?= =?us-ascii?Q?pjoqnYJyzVppDKHtEIg6Yp84PQnBx10Vm5Q+bBfxSkpUNBc7qdqWB4fj34my?= =?us-ascii?Q?c2n3NtWlfUtRT52vqz+agEzXgI7batH7Qz6gS8/F4CvrzZNhzZfKEi/5nk+j?= =?us-ascii?Q?QTwAgRgxCtT4VBYhz2I0l9wKPG0U84YQ3EvpKaKxCyxZYlVzJrY2MSkgQDlL?= =?us-ascii?Q?enJx3KVS9I7+b8Yjcfq/wQmUg4y6frY3NDDUoFtjhQbFK5Kxkip74S9RJY8r?= =?us-ascii?Q?HOp4min4dsdd16ebPCWZsfQXHUxeFuHsAuQ8ZVshuhrwlVIV3otlZSprYA32?= =?us-ascii?Q?gl8ImHaNGwagyb4GkPJMYcN4DAM1l6oYB7lG85yny+xBIDGyxyG1wN32tZpD?= =?us-ascii?Q?G8wJw7Cw8Xit1ChHngiGqEU+C/qbCtM7vNVyNrNJyP0KV0HMToIP8BUCYFsr?= =?us-ascii?Q?YkH+574ap1vxgSpfWf7uYkcAToFlkwDCI5yFxfprYwRqyCq6SFmUXgI8B7PH?= =?us-ascii?Q?3pRU5BcWCmJlflkzGzG0UmxYJr8YlSLMUK9v/pjASC1j5s4ZQHtyEaJFdq65?= =?us-ascii?Q?tP44RdtgGnR9Z27EZACc5TivGsi3KJ18tJf1cxFVJ/y7Qn/giKx98h1z+FUo?= =?us-ascii?Q?o/8zA2d+ooYEqPqah/GNGJ32eeAyIc1KjupBFmg9RYwF+grkAyhj1k80jWUA?= =?us-ascii?Q?oWa+W5CaQ7fERi3eo2ckiDecThYw1cptPT9QsH7OaP7nvczLi6pRis16m6ER?= =?us-ascii?Q?31i+CHy29oSRugCbwPOYvYRoSgiABY4QbEjUVR6nkd5iJFZ59jZXv6AC7Hr4?= =?us-ascii?Q?E6yvGoYEBFZ8+PpRdnn7o/08AMHOCuZ93+PSQ453dNME81n1blVytbzm6hnP?= =?us-ascii?Q?OnO1YR3exDM1+EmtX5/tBWw14hAX0aflQ7xYoAqNHYwvsNv2wlmgiI1YnAXT?= =?us-ascii?Q?7evNju/zQ05TMTU1NTQvZouAamxPMk36OdXrc+dBJsmvSoT9aVNhuMT0kgvw?= =?us-ascii?Q?wrhFC6edV/CyrORjY3JnZAAOxb8FpVdl78bRSaSazeozNGkoI0ThEiaguZWP?= =?us-ascii?Q?2Td0h5Fc0idMoCfWGfrxBHZLtRqY4esDg6/bLk23xf+P0UiwyJINUAirvb+e?= =?us-ascii?Q?UaKBI+IE7RCNDcIgsUaq+8J5gkYAzlD1U6tPTOHwS6pnAEQQIPieR5h+0v2i?= =?us-ascii?Q?ezpNcw2w9BU27ONLAEsFh+eJS6JpL1p4sfcoeFv5JofsItx8OZb4VacgMXO0?= =?us-ascii?Q?FqnVRBC0EaVe/smUcUGrALCu0nPRfvwQqD5wLOdvt31vJe2ViDRD6+J6HhsR?= =?us-ascii?Q?iYtXhP4/HsAEhkg=3D?= 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:(13230040)(36860700013)(7416014)(1800799024)(376014)(82310400026);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Jan 2025 12:47:22.4928 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 2cc5a2e8-e4fe-4a34-15b4-08dd2e5043d3 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: CY4PEPF0000EDD6.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH0PR12MB7837 Content-Type: text/plain; charset="utf-8" Secure TSC enabled guests should not write to the MSR_IA32_TSC(10H) register as the subsequent TSC value reads are undefined. For AMD platform, MSR_IA32_TSC is intercepted by the hypervisor. MSR_IA32_TSC read/write accesses should not exit to the hypervisor for such guests. Accesses to MSR_IA32_TSC needs special handling in the #VC handler for the guests with Secure TSC enabled. Writes to MSR_IA32_TSC should be ignored and flagged once with a warning, and reads of MSR_IA32_TSC should return the result of the RDTSC instruction. Signed-off-by: Nikunj A Dadhania Reviewed-by: Tom Lendacky --- arch/x86/coco/sev/core.c | 39 ++++++++++++++++++++++++++++++++++++++- 1 file changed, 38 insertions(+), 1 deletion(-) diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c index 00a0ac3baab7..f49d3e97e170 100644 --- a/arch/x86/coco/sev/core.c +++ b/arch/x86/coco/sev/core.c @@ -1428,6 +1428,34 @@ static enum es_result __vc_handle_msr_caa(struct pt_= regs *regs, bool write) return ES_OK; } =20 +/* + * TSC related accesses should not exit to the hypervisor when a guest is + * executing with Secure TSC enabled, so special handling is required for + * accesses of MSR_IA32_TSC. + */ +static enum es_result __vc_handle_secure_tsc_msrs(struct pt_regs *regs, bo= ol write) +{ + u64 tsc; + + /* + * Writes: Writing to MSR_IA32_TSC can cause subsequent reads of the TSC + * to return undefined values, so ignore all writes. + * + * Reads: Reads of MSR_IA32_TSC should return the current TSC value, use + * the value returned by rdtsc_ordered(). + */ + if (write) { + WARN_ONCE(1, "TSC MSR writes are verboten!\n"); + return ES_OK; + } + + tsc =3D rdtsc_ordered(); + regs->ax =3D lower_32_bits(tsc); + regs->dx =3D upper_32_bits(tsc); + + return ES_OK; +} + static enum es_result vc_handle_msr(struct ghcb *ghcb, struct es_em_ctxt *= ctxt) { struct pt_regs *regs =3D ctxt->regs; @@ -1437,8 +1465,17 @@ static enum es_result vc_handle_msr(struct ghcb *ghc= b, struct es_em_ctxt *ctxt) /* Is it a WRMSR? */ write =3D ctxt->insn.opcode.bytes[1] =3D=3D 0x30; =20 - if (regs->cx =3D=3D MSR_SVSM_CAA) + switch (regs->cx) { + case MSR_SVSM_CAA: return __vc_handle_msr_caa(regs, write); + case MSR_IA32_TSC: + if (sev_status & MSR_AMD64_SNP_SECURE_TSC) + return __vc_handle_secure_tsc_msrs(regs, write); + else + break; + default: + break; + } =20 ghcb_set_rcx(ghcb, regs->cx); if (write) { --=20 2.34.1