From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.remote-ip=192.198.163.16 ARC-Seal: i=2; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=fail; t=1793937972; b=0/lV5T0h0RBVI2IBK0vY0dq1aRzQVwuK3ydqQ+GY06X5CVt59W2nw+Sr2lbxs0IsDo2o 276lGaILC7bPcJZydRahqPbVga5G3GdX3sZqwCAWw/fTtEe11eu7w3pqxVoZVivQjgJ5c +T09BcscGjrf9CV6QKG4eVlQJmvym2KNCgWH5KCToAcgXxoYnXvbJ5rZkCm3bDiW96/9U phxkpYLDvU4JV+hlDGUvZ0ptgHJG9m3xZrhF3XlTlWXjjoVTCmp0qYdYdNljiQ0m7H+24 lhyGABPb2rvc2LLfHnrMfh2TfrXl+YjFK9hab7tOGqZDNzAOPF0sQyXGmYX5dbj9ehw== ARC-Message-Signature: i=2; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793937972; h=DMARC-Filter:DKIM-Signature:X-CSE-ConnectionGUID:X-CSE-MsgGUID: X-IronPort-AV:X-IronPort-AV:Received:X-CSE-ConnectionGUID: X-CSE-MsgGUID:X-ExtLoop1:X-IronPort-AV:Received:Received:Received: Received:Received:Received:Message-ID:Date:User-Agent:Subject: Content-Language:To:CC:References:From:In-Reply-To:Content-Type: Content-Transfer-Encoding:X-ClientProxiedBy:MIME-Version: X-MS-PublicTrafficType:X-MS-TrafficTypeDiagnostic: X-MS-Office365-Filtering-Correlation-Id:X-LD-Processed: X-MS-Exchange-SenderADCheck:X-MS-Exchange-AntiSpam-Relay: X-Microsoft-Antispam:X-Microsoft-Antispam-Message-Info: X-Forefront-Antispam-Report: X-MS-Exchange-AntiSpam-MessageData-ChunkCount: X-MS-Exchange-AntiSpam-MessageData-0:X-Exchange-RoutingPolicyChecked: X-MS-Exchange-CrossTenant-Network-Message-Id: X-MS-Exchange-CrossTenant-AuthSource:X-MS-Exchange-CrossTenant-AuthAs: X-MS-Exchange-CrossTenant-OriginalArrivalTime: X-MS-Exchange-CrossTenant-FromEntityHeader: X-MS-Exchange-CrossTenant-Id:X-MS-Exchange-CrossTenant-MailboxType: X-MS-Exchange-CrossTenant-UserPrincipalName: X-MS-Exchange-Transport-CrossTenantHeadersStamped:X-OriginatorOrg; bh=H2UHDGQI3QFiENKEUoqGc4PhReuEo1I8O5u6JAOmvCU=; b=A7oQkVozkYlFGEwXdZbukjBRTKFeeurQcVK6I1qZeABzsuSoTxjSBjEwckW+Onf8Esq6 PMb2TWBZa4BrTIZSpor7+Jyj8nOwc2VhOKlFonXOfM+alPufz8yzN/Fizy8dQA2rocdSe G9Pytp2OiqqWd2ujeNs1PN+qmtkXczpAZEHivQUFzRQXNlif9p2GhxmCFTqFMFH4KVbax MNhuqtRD87ByLPFGXHebzDuohne1ibEkRxVSkwXbnE1j3xeVmtZ7ghOiTO8TSDohZpWw9 OoNldwVEeKyJxcmiJm6XaZ8eYnHvgKzQs6RDj9qfvjpp0wuSYrVYMaEm775oAh6So0A== ARC-Authentication-Results: i=2; smtp.subspace.kernel.org; dmarc=pass header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass header.d=intel.com header.i=@intel.com header.a=rsa-sha256 header.s=Intel header.b=MMaKs+PN; arc=fail smtp.remote-ip=192.198.163.16 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.16]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5649C606A326; Fri, 6 Nov 2026 04:06:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 5649C606A326 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=intel.com header.i=@intel.com header.a=rsa-sha256 header.s=Intel header.b=MMaKs+PN DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1793937971; x=1825473971; h=message-id:date:subject:to:cc:references:from: in-reply-to:content-transfer-encoding:mime-version; bh=DOF7Eqo87wlhSBl2rY1r3rdofOV/HzScdSg9Lz5xpy0=; b=MMaKs+PN921ivZwGCrTJTaLHmj31wcOHnCaJrsMppTzjCzFOcRErVrN6 zH0/31RZHJtRYeDy6hRdNQHOZe7o+ED9M5qgpRheANW7vxqCC+sh/qRTO XlmwvdK4kBVPhy/vc9YvRvydiK3+1qW5sOfqBySo1UsYSqKZba5VP+Hpn yn/+liomnBjvebtVu0mTFyYz1mKwJaQIEFLNN8Z8MoCWj+X4+Qma6y4G9 tFMapGC6Kdk3oHt6O/NnfHBEQgzzNFLSU2kp31V9Bcn8l47o8Mwy+hKT7 P2R20GCO4nJSrpHgnzvd5fhjH8CvinJ0ruK5KQrDMyzaEd3Ft2lUKnVMA g==; X-CSE-ConnectionGUID: k3IHSSTsSDKl9rw9+LYbMA== X-CSE-MsgGUID: KbWEiFWFSuSxvLbXtPfVyA== X-IronPort-AV: E=McAfee;i="6800,10657,11957"; a="2770079" X-IronPort-AV: E=Sophos;i="6.27,197,1787036400"; d="scan'208";a="2770079" Received: from fmviesa011.fm.intel.com ([10.60.135.151]) by fmvoesa110.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Nov 2026 20:06:10 -0800 X-CSE-ConnectionGUID: qQ8/jEbLRuGXJESxTbyrXA== X-CSE-MsgGUID: xxiX2YODSNGDoyn6KydJuw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.27,197,1787036400"; d="scan'208";a="8943413" Received: from orsmsx902.amr.corp.intel.com ([10.22.229.24]) by fmviesa011.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Nov 2026 20:06:11 -0800 Received: from ORSMSX901.amr.corp.intel.com (10.22.229.23) by ORSMSX902.amr.corp.intel.com (10.22.229.24) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.56; Thu, 5 Nov 2026 20:06:09 -0800 Received: from ORSEDG901.ED.cps.intel.com (10.7.248.11) by ORSMSX901.amr.corp.intel.com (10.22.229.23) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.56 via Frontend Transport; Thu, 5 Nov 2026 20:06:09 -0800 Received: from BN8PR05CU002.outbound.protection.outlook.com (52.101.57.38) by edgegateway.intel.com (134.134.137.111) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.56; Thu, 5 Nov 2026 20:06:07 -0800 ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=rV1ZYFj+FN7y4HZNfSEcmBVyHG00Xf9LSXF0SPZ/EgCorn94cNBbg3N4fa0+pJZST0ku68XQMcGVEyssqOom5dmFrJpnQSjFv5SoJFnUVuc67J5/DyxH50/PHMhKgrOVqjpEnbwdvRFJ8H1hH3UfjVkjkiJgYefwl4XpxiBM4QvHj1HycWpAnu/0+VqHnF+91x93FxanGsQsLreeRo7NG9ysoLuG1mAvdl46Q83QzRpraXzbRfVIAwTxaTq5HmRKgtWkLm+8yDW44aVU0Q5eIyw6dX+T1mNkQ7hq+fMZz8Nk0erV8+qU1f0yT62I0DIQCjuOZM43nU7sS6U/l2t/rg== 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=H2UHDGQI3QFiENKEUoqGc4PhReuEo1I8O5u6JAOmvCU=; b=lPQciPeWA805dLusjyjD2+8Ejfgayj+3pH5grqAPdg7MOhKJ3j6h8wien7pobiuwFsOhUV6QdNj1+MnaxsnUmvliOvvsoraQItiixDEMPh8zUAkn5h+F+20NQ/1iFpAjwY2AhFyT7rg6fT6AdwjeOx3TCYNdfuyQisiY0SsgA8MZR2r5R3d93a9KcBK2HpBCjnIhzgTFw14z5UBDxH4pUUz+SgqLED6CoCtrAe87euSpR76vENXLVa9Q/DpTgitvtiQyxNBEgcTqvhdpKLyUMVdO/WQPA9qBapFmRmOdgH8yc6tQwgeeaNaQcU0qHtTYwSUUt5twsQgVfYpem4IBIw== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=intel.com; dmarc=pass action=none header.from=intel.com; dkim=pass header.d=intel.com; arc=none Authentication-Results: mx.microsoft.com 1; dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=intel.com; Received: from DS7PR11MB7857.namprd11.prod.outlook.com (2603:10b6:8:da::17) by DM4PR11MB6382.namprd11.prod.outlook.com (2603:10b6:8:be::18) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.592.10; Fri, 6 Nov 2026 04:05:57 +0000 Received: from DS7PR11MB7857.namprd11.prod.outlook.com ([fe80::3552:897d:29f7:e0e5]) by DS7PR11MB7857.namprd11.prod.outlook.com ([fe80::3552:897d:29f7:e0e5%3]) with mapi id 15.21.0592.009; Fri, 6 Nov 2026 04:05:57 +0000 Message-ID: <207a498f-6bd6-4e9d-a050-eee863d25237@intel.com> Date: Thu, 5 Nov 2026 20:05:53 -0800 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v10 11/28] KVM: x86: Add a helper to detect if FRED is enabled for a vCPU Content-Language: en-US To: Binbin Wu CC: , , Paolo Bonzini , Sean Christopherson , "Jonathan Corbet" , Shuah Khan , "Thomas Gleixner" , Ingo Molnar , Borislav Petkov , Dave Hansen , "H . Peter Anvin" , Xin Li , Andy Lutomirski , Peter Zijlstra , Andrew Cooper , Tom Lendacky , "Nikunj A Dadhania" , Shivansh Dhiman , "David Woodhouse" , Chao Gao , Zhao Liu , Yosry Ahmed , David Matlack , , , References: <20260911213659.2025974-1-sohil.mehta@intel.com> <20260911213659.2025974-12-sohil.mehta@intel.com> <60f7934b-5271-4207-b071-6240b5d36cc5@intel.com> From: Sohil Mehta In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BY1P220CA0018.NAMP220.PROD.OUTLOOK.COM (2603:10b6:a03:5c3::8) To DS7PR11MB7857.namprd11.prod.outlook.com (2603:10b6:8:da::17) X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS7PR11MB7857:EE_|DM4PR11MB6382:EE_ X-MS-Office365-Filtering-Correlation-Id: 3e32295b-1e52-4546-6500-08df3bbb4284 X-LD-Processed: 46c98d88-e344-4ed4-8496-4ed7712e255d,ExtAddr X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|376014|7416014|366016|1800799024|261022075727099003|261026140227099003|11063799006|4143699003|261009223027099003|56012099006|261021121427099003|261028144727099003|261022105027099003|261026121527099003|261102123227099003|10067099003|18002099003|22082099003|6133799003|3023799007; X-Microsoft-Antispam-Message-Info: tPacwIQkZ4y/7nhBXQzIuVCmY8dz9PJ63a2y/4aYFOJXtE1NIHGnOrBVTvaejCxYkIwA09O4Tdzo8vaynX35jvwDREBiePB6s4WHnfwGOmu3agwTNPEAP1/czV+wsculs8lbXZGrrOTZKm6s7OT8GWCcC4qlywtC0BwjDEh47oCaaOBwYXhZ6B7jxtOqmclVp8P3uh7dCDWjs7JIdqE6jY8zTSWJ6XKIsBeRhi4p/hd0xQs20wB6Sg6IvlqR2bZsf9/mFtVgdhTuR1568lPnfpQhNXwBmpN1cCquSux+mT6dGYYvsJNnjE5acM+5v2LPSL4jxpWF+nmgqlgicQY3ShJcksiXrxaeBd7lT3oEj55FWH4yV6Y95nmHuVVWnSn+Djm1vMwK6nE9nT4WkzTtOaguSzETH3cIu2AZV3EceGs1UscR0y5uoC8QNcOc8WKiUc1iFCIH13C2pzh5F1i+le4R9tXCAzEVSs3n+old9KvG+6Q5PLEpn+nAuCSlSOGtq3Wzi87mxGNHXC9+rjaVr0c4xTazE/A7l7f9oKf9IK5rYCaLI8jWCy9b2KBEN7/7HpIPH8eF/UbXHyDQCQwQYGW8SPwFuUjr57zZNsPHjBHJjug8vqDwF1/YdMki3wx+xewCUL4+rS3+OJZAB6H9Zr88ByeDlc538kREo2Ub8rE= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DS7PR11MB7857.namprd11.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(23010399003)(376014)(7416014)(366016)(1800799024)(261022075727099003)(261026140227099003)(11063799006)(4143699003)(261009223027099003)(56012099006)(261021121427099003)(261028144727099003)(261022105027099003)(261026121527099003)(261102123227099003)(10067099003)(18002099003)(22082099003)(6133799003)(3023799007);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?ZGFSR3dmVS9JYUt1eTF1aGNtVHFOSW9hVEVoMGp0cW9BTy9rUm9kQVkrcXBq?= =?utf-8?B?bGJwaFk2MkJlcVhSR2NROWZzaDVUN2dLZDZVcHhjWERVVDZWdCtPWHYzRzhs?= =?utf-8?B?ait4UU1mWVNQZWkwZ2Z0cGc5UWhRbjQ4UGN0REY2WEZtM1liN0xVS3owaHM4?= =?utf-8?B?dGVaRVVFTG1KQ01rYTJXUVJyQ084QlUvcG95NTJlMXFmK1NZNU9MbjUyMFl4?= =?utf-8?B?MGtkbTUwUGwxRjZjYlVDNGpuOGpxTENEMkJjRnlaL2M5Z3BvU3M3OHlDazB4?= =?utf-8?B?MDFNMW8yL1EzWGczcWtFZ25OSi91TjB5MHlJL1RVaDZNblMwNFJNaE5sR0Z6?= =?utf-8?B?dHJ2S2hlMFBGTWFya3NianI0UkdVU1NuTlV2MURpem4wbFowM0NtSjl0a1ZN?= =?utf-8?B?QVhuMmVaaXZXamgvT1FHU0VmbFVrWWpraDhpSDk1TlNTUCtmRXU2SjNud0k4?= =?utf-8?B?NC8zZi9GVUYyNVJ4YjluZWJiRWE1STJHZkFRdVAxN0tVT21IcDhUTmcrZms2?= =?utf-8?B?U1d1a21xMzl6VUs1N01CbXo3Vno1ejMzSUNyNmxFOFk4S2FjVlllcU9CV3N4?= =?utf-8?B?THZCVThTSVYxT1VFQk5hMys1bnpqQWhhSnBOeHlHTm5GSTd6TTRKcnFiKzFh?= =?utf-8?B?YlF0eFI5dllFY0xvVkgxQkxsT3M1Q0E3K0gxVENYekN4WE0raWN4a2tLL3E1?= =?utf-8?B?dDhSbWJoL2p2VGVBN1dtOVpNQ0FYN1E1WnRlMVNZNlZ6eXRQTEpZTWUzQnp1?= =?utf-8?B?YTh6YzRCRGNxc2JxMXVLelFXWDg5NDh4SnFCV2JXVmhMWVp3cHYxUzNyeTR3?= =?utf-8?B?K1Bwa3ZpWGY1Z2o5MlZ2RXhCd2ZHRTlUd28xQVhVV3BqaXNsSjk1Z3pMcGJa?= =?utf-8?B?UzRFWSswdWpBRlowSUs1aTVSVGRDWEdzSlBaSDV6V0Qvc0lrNUowQ3BsdVhp?= =?utf-8?B?ZWkzTWdaellnT3dxaUhHaUk4SEwxVkpGL1pRNHR6SU5meUZSVkhJR3A0Q1RZ?= =?utf-8?B?YWo3eTJ2cVFENkpvSGJDZDdIQzE5cVJna1NlNzRMZUtVUDc5NWV5TFVDQk5N?= =?utf-8?B?NkN4bVhadERnN0N1ajI2U1Y0VWF0S2FEdTEyNFNnNi9jVjVWWVlSaXR5NlZT?= =?utf-8?B?V2hsNFFjSDlhUHJPQ1JPMGl0cmNDYzFDeHA0eEhKTE9qM0lKaSs2QkwrZDBy?= =?utf-8?B?OCs2L1B5MDluSzZGUVMvdnBLNTB3dHlReUI1TzdsRm1Bb2JNNmNPQnkrcTRu?= =?utf-8?B?eTBmcWtraDNpZmtjKzNFdmlCd2VYSkYwWnNldEFVQ3Y4aDVjRERRaUcyK00x?= =?utf-8?B?ZVJXOFJtanhWQVFBVUF6cGVYSmc2bkRWYkRDS0F4dUFYQmt2NW01YUo3clNu?= =?utf-8?B?YmR2NlZGc2tBVHlMTjY3cFFnMnlNZnhkblNENUNwVVBkR3Zoa1hsdnA0bVhM?= =?utf-8?B?dU9FTmwrNk8vZnUxc29VTlIrbGVXM0t2MDZJNVlHR01nSE9wamdsZXdNZDNX?= =?utf-8?B?dEo5MjZMNXdqU3Z5anJwdXhyQVQ3K2VhZVM5aHVDSlMwdWFOanRZNkpHcUtL?= =?utf-8?B?UlhOZTVqS2EwdFF5OEgrVmxlV1N3d2h3Z1NCbkNJRFVVVWJPQ0NVZkRVRUtY?= =?utf-8?B?OXpKVFlOVEtrOG0zSFQ0TW01UmhIdWM5Tm0zSFlJci9UVVhialhSMjA2VHpE?= =?utf-8?B?ZE5vKzhUQ1REaEJ3c0JtTG96MWhvU2UwdjlDeDNjSGY5RHVYZ3JMd0Y5d1pz?= =?utf-8?B?YzNCVnZURGpzcElvT2RLTkw1eUZGSnFqUHVmenQ0UVJqNGxlWmJmTkFLK0Nm?= =?utf-8?B?dTUyS3pJYTlZM1NzeG5NdXBreVdyL0FwenBLcU9JazRMSUhyTUQvSmY2Z3FL?= =?utf-8?B?TU16NDczT0lwU1Zqc1FUMWZxSGl3bm9xVFluU1pHYmduaXYybTBMWTIyVHBr?= =?utf-8?B?UEJBZzRNY3ppc1dRUU5na1I5ZitHS2wrRjhLUC9Xa3FxMzk3WHB5VFJETGR5?= =?utf-8?B?emRnancxZ0oxOUo3L3RqRTVlY1NqckNWMXJhcm1nalorUUdzd0hxT0R0cGtr?= =?utf-8?B?TzhZMHhhV2ZWdDVpT2ZKeDVUTy9vMmMvekJZZVk1dHR0enlNWTBRa3Fobm1U?= =?utf-8?B?NnNUdFZYMGhkZlJMZ0YyQ3QyRlhpa1l3ZVlEQzQ2K1NEbHJVQzk4cG5uZmhS?= =?utf-8?B?U2pVYkR6WjFFSzh4Q0tJemlBZHhQM0VxZmx0UHQ1Skoyd0J5cVJCYXBlYTc2?= =?utf-8?B?cW9FQjNJSEw1amVxdXEzT05rWFpmaUFlZkFpS0hVSG9nekE0dHpyOTQ2bkFQ?= =?utf-8?B?RzBOa3J4K2JGWnBXZ0hSdFBxY0pZRUxVSDNBWHdzb2R2YmlqR3FSZz09?= X-Exchange-RoutingPolicyChecked: sPBRdqi0/NOqXbrYXA3MpyBc3PALwn2sZsLRftEH2V+05NtR4Wzxqjq6Q6tu4o4LddmSLYbuYu1V7ThtWLeVPFj0afoD17JPnBwG8hRGraFsNFdd8ygw3PArxyLEW7Lfb02lnejCu3m03bj4in5KuQok7X2u9wsisJwoK4Qu9pjUmbcvSuBPVyhC85MqJszkH86d+H23U9NA109nwRxcxp0tBM0mdFP49U+a0K3rfY7v2FpICrbVmjH0blSvUpUnj1EqmbRoHNFo26zz/TlqsOZ+/DczXBzRndRtSJQ9Lrdo7+koSwUAkamhAZweEVJ9bQ/lTZ8tO9wZQLVMddYg6g== X-MS-Exchange-CrossTenant-Network-Message-Id: 3e32295b-1e52-4546-6500-08df3bbb4284 X-MS-Exchange-CrossTenant-AuthSource: DS7PR11MB7857.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Nov 2026 04:05:57.2946 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: QHX/8QXbZ247jQWiTcjFf4tq5iYPeBOab9jwk900Ug935nsQbNXYSwFQXZjSMJZKJ6bNq2MMRen+S3EsSxpZaA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR11MB6382 X-OriginatorOrg: intel.com On 11/4/2026 9:16 PM, Binbin Wu wrote: >> Is the suggestion to add an explicit check in kvm_set_cr0() that >> mirrors the PCIDE one? But there isn't a fault specified by the spec for >> this case. > > Had a second thought. As you mentioned below, if em_{jmp,call,ret}_far() is > triggered and CS.L is cleared on ring 0, even KVM doesn't check FRED status on > far transitions, the next VM entry would fail. So I think it's not needed > to mirror the PCIDE for FRED in kvm_set_cr0(). > Yes, agreed. I'll avoid the check in kvm_set_cr0(). >> >> Sean also requested negative tests for things like leaving 64-bit mode >> with FRED=1. But, I am not sure how to test this. > > Maybe it can use KVM_FEP to force the instruction emulation in kvm sefltest > when force_emulation_prefix for KVM. > Okay. I'll add a FEP test that validates the emulator's far jmp/call/ret behavior. >> >> AI tells me such a mode change can happen with emulated far transfer >> through an MMIO far pointer. "em_jmp_far(), em_call_far(), em_ret_far() >> and __load_segment_descriptor() have no FRED checks, so none of them >> raise the #GP that FRED spec 8.2 requires." >> >> Chao had brought up enhancing emulator code and making it FRED aware >> [1]. I am wondering if we should revisit it? > > Without the check the next VM-entry fails the guest-state check according to > FRED spec 11.5.2.3 ("If the DPL value in the SS attributes field is 0, the L > bit in the CS attributes field (bit 13) must be 1") VS. With the check, raise > #GP instead. > > Not sure about the maintainers' preference. But a check on FRED in > __load_segment_descriptor() looks simple though. > I am inclined to add the check as well. So, I'll include it unless someone says otherwise (or it gets complicated during implementation).