From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.18]) (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 C2F402DEA90; Fri, 1 May 2026 19:13:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=192.198.163.18 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777662797; cv=fail; b=nd80JoTJGUnXIAJjjhV2pDyTk+jktgCkaKcpqjP9ldj3JfB4qk0lwJemqFa64nNtl4T4+WO5wOpeMPMc2/tk1+7pXCCAr6JqLQKEM52Jeo/HktKa1+IMvYtZuEHnpHB0ihuckR9XCT3CLJtRMLq5ZemPvGvYi1uPZSiP711pKu8= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777662797; c=relaxed/simple; bh=GmRaA7BLAgD8YRkSw/hpsoffVytNmz2lQ8z+scnwfB8=; h=Message-ID:Date:Subject:To:CC:References:From:In-Reply-To: Content-Type:MIME-Version; b=Etpa5eXPXSrZFwuMms3BLPs98n+/ZeLddr4gBtp+l/+Wny+HwWDVvY5qSs+bKLgsTDOKJePjJifLKL7P/PLdtK82jKK1U6R++QOAdQzpd32XDjWggjndR64oNlXiUJx7jiIK//3QKJ1Dc80n9sw3UGVTQrIx+VKr/6Ae+CUt4MM= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=BEilBgIY; arc=fail smtp.client-ip=192.198.163.18 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) header.d=intel.com header.i=@intel.com header.b="BEilBgIY" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1777662795; x=1809198795; h=message-id:date:subject:to:cc:references:from: in-reply-to:content-transfer-encoding:mime-version; bh=GmRaA7BLAgD8YRkSw/hpsoffVytNmz2lQ8z+scnwfB8=; b=BEilBgIYn1LncxQzSyzJBSLKshYBOsyXqO4kHjfPAU5u6qPPsoq6eLF/ /EsfVcvnHnlXof7wqHyVDFkk8JUGAuRdT1qG9rt1AtZuoP19hLqsFr7hX IkB9nTHYki69zwBFyUYm3frMTanyEd7Mkno2AC0ozQAZa4IE4nqCAXAL5 UhVgzBVWNzLTP4tfVXkwbRDnJ2uKST0AXlbmtiAgMiH+HVfhiROjB1WgD Xj3ztiUPWMQjPFFmKyvYm5K+0jKHJv9dkb9XbF0iU4sMBz+l7g9JwoDJJ Q/dJky3blzMQuPIH75OmsnMYAfB/DCs+NQGDVidDm+rq+BzUsQvt1I0Wj A==; X-CSE-ConnectionGUID: uSTHOfsgQQ6G2ghnJfoEMw== X-CSE-MsgGUID: 7u4HVKtpQNmfmMmm09aEAg== X-IronPort-AV: E=McAfee;i="6800,10657,11773"; a="77787505" X-IronPort-AV: E=Sophos;i="6.23,210,1770624000"; d="scan'208";a="77787505" Received: from fmviesa008.fm.intel.com ([10.60.135.148]) by fmvoesa112.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 May 2026 12:13:14 -0700 X-CSE-ConnectionGUID: GFBXXBeFRAK9WF/kipyB7g== X-CSE-MsgGUID: 8/wyCm9TRiGKSusTeFhTQg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.23,210,1770624000"; d="scan'208";a="232294054" Received: from fmsmsx903.amr.corp.intel.com ([10.18.126.92]) by fmviesa008.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 May 2026 12:13:14 -0700 Received: from FMSMSX901.amr.corp.intel.com (10.18.126.90) by fmsmsx903.amr.corp.intel.com (10.18.126.92) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.37; Fri, 1 May 2026 12:13:13 -0700 Received: from fmsedg902.ED.cps.intel.com (10.1.192.144) by FMSMSX901.amr.corp.intel.com (10.18.126.90) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.37 via Frontend Transport; Fri, 1 May 2026 12:13:13 -0700 Received: from CH4PR04CU002.outbound.protection.outlook.com (40.107.201.56) by edgegateway.intel.com (192.55.55.82) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.37; Fri, 1 May 2026 12:13:13 -0700 ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=DCZTpHAwFFZnH45NFWiUWySUbsiNwDCE/W1evauPqvTpbTkyDchjKy0wzYlV/9MNrM2WtNJ+cLGl97hhEdgx9+AkAb7y0J4qDpwnMMAKyhHhUJcbIaSyAuC1Cq5u1Cp4jxQYWt3XhtUr/Aq41+4W4qK5EfaY20R7TnncHHvNhscOEhjji88KaNtT60xzObhqQnZODmid4MfkhmNParN0+C1IYotQZl3svhppLHwUsFvZN4Wy1tm5Xcfkqa1QM+G925LiTcciN5I0O25q2WG+Oc/hKVz5oTDqtkV7nxsmqeaV8J30vmc3BYFnltvl6GIM/tKEITPIj8amZhuV55uNww== 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=EcdNkrKa8wPWbuPjXVijYAFguRywX9628Iv2MchHuQI=; b=B9Xrc6k6e/v98shMxvls5B7Y9SsGpn11hmjj/bGnb56FlCOhdotDN9FlAftDXBTe8DKDZq1OjP5FSJc/nzh967rqQqV46gPfb/2OfuGjgwENeGr1yaTcR6FW1ixblGapk1eLhxPuz82cGcA2720wL1RP3ShCK/duLPV1HycevNg58bEqA5lQhPu0tUQXRZW8NH3K7f9Ro1PrEWbZoJfMo9Fi6bg3zjHO/L/riGfK7O1nIBcemVNJcTtjbKbVoyoznkpOUwrEXnSZHQbT30YTfgQ9MiFc3jpuQfKpRdYXUG3bqmcr6Lr4lmhoH3/rMH3vdjW4v9LandLBTEzG+GXA1A== 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: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=intel.com; Received: from DS0PR11MB7925.namprd11.prod.outlook.com (2603:10b6:8:f8::18) by DS7PR11MB6222.namprd11.prod.outlook.com (2603:10b6:8:99::20) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9870.21; Fri, 1 May 2026 19:13:10 +0000 Received: from DS0PR11MB7925.namprd11.prod.outlook.com ([fe80::60af:89a0:65dc:9c84]) by DS0PR11MB7925.namprd11.prod.outlook.com ([fe80::60af:89a0:65dc:9c84%3]) with mapi id 15.20.9870.022; Fri, 1 May 2026 19:13:10 +0000 Message-ID: <02a4adb3-8829-4681-b170-e3a2f44bf11c@intel.com> Date: Fri, 1 May 2026 12:13:07 -0700 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] Revert "x86/fpu: Refine and simplify the magic number check during signal return" To: Andrei Vagin CC: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , , , , References: <20260429000623.3356606-1-avagin@google.com> <7c2681ee-a53c-402c-8947-e7a74f8720c8@intel.com> Content-Language: en-US From: "Chang S. Bae" In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BYAPR03CA0021.namprd03.prod.outlook.com (2603:10b6:a02:a8::34) To DS0PR11MB7925.namprd11.prod.outlook.com (2603:10b6:8:f8::18) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS0PR11MB7925:EE_|DS7PR11MB6222:EE_ X-MS-Office365-Filtering-Correlation-Id: 64d65fb4-8828-4bb6-da72-08dea7b5aef6 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|376014|56012099003|18002099003|22082099003; X-Microsoft-Antispam-Message-Info: ERgoai4LgqxXP0o3mLBfkg/27LYR/a+yVisPZ8oo7LaJd85Wp3aJ1wJOSlmRN07KNkeCirUHYxQ6dfhna8p3LKQ+F4E4XP+hBUR5jtA5frs3P6GDYmdJHtihZLhpuLMW/gBVJLY1B8hhhO5cd5Rr6Q3W3kwniRcUjacSGcfQAu6OjYsbOrmaW3niFGT7AOnzUWtRbyK2004jUXCdkqzP/009sj4gb7L4NJoHol744OEDxf0ivwxVGm1TmMP0qGS4q3O63P/7vHz7j8jvr9IkMkkjD0CPyPqASlWgIZeGN+w2FRln6ddLO6gnx7p6QY5NkKU6rnXpkxWFRlLjFbZE7tcrx45XTFOCnSN+uq+ZFQzqlCarKBd7928+JLqXcUgi/NPKKDNkOPA8hGVc80pdpBHsk2WOE7QJI7D4QJTBtGSTnctRlvtta9tLs3zkA2FGmGJwNx5whon0VCGyUZQNlsn3ur2K6TZsRfaMdt1H4Z7SN+h4lZiGMxOgVYb8TO2ivZ0FDARnCoasa64FhYjPfPvdFMeyEBuC3n6lf6ZA50tvTRGltV4E6I0YOv44JPntdI5OOZOb3lm97jBXwIJVdCZP95i+AtdH6aNxIdlMmWnk8xmnS4gOtFhhklny+rCorWXs0EpsFryT5vMQ32fHcBiKuQiBQWVUe49osnFHL0cnguzgtnmNwCvugsoNIutd X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DS0PR11MB7925.namprd11.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(1800799024)(366016)(376014)(56012099003)(18002099003)(22082099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?YkxsWXlDbHprTmdRK0FZVmFNNlRIWVVpa25WNWtkZDE1Y095bkJ6MFdORDUx?= =?utf-8?B?SHF6VzF6VWplZms3a21aNU14VlRpajh0c0VqT0pmZGIvMTg1akh5THFSL29j?= =?utf-8?B?UmZKTy9OZy9vV0M0NjVxb2Z4T3BHOVpLZXFVVTFxRHYzc2VPMXhKYk1MYXFo?= =?utf-8?B?T3VDWExhb1lZK3UzbERXNjlrbCtUSDVXeXpWcjdDYUhNakJneS9CVEVFZ2dK?= =?utf-8?B?cTlXell3c0dvVkd0cXpCRU02djNkeWpjTlBLUTFvNU5lbzBOem5wUE9KcWFL?= =?utf-8?B?VEc1YStnTWdXanVFZzFySHk4RTJSd3E5ck0xK0lsUlRuSWJrdm5iWGtBb3VX?= =?utf-8?B?T0ZNbmRWbEhlcmdCTHpPTFBnWHRzeHE5ZUpwblBMSkdtTGFwYTc3M1FqVE9M?= =?utf-8?B?YVB0aVovelFaaEpVUGJYSnhaMmlZKzZSbjZHdi8ramFhU1laRnp4ejZwRnJM?= =?utf-8?B?SzlJZmQyaklnSitpdWlmYW1Da0FQVm5WdndaSEtNMFBId2duOU1jRlFBZk1k?= =?utf-8?B?Z3ZQdEY1WXFEU3RtTHRKM0E4OUEwcXJac1VYUkNtRFNqRm9MOGVjUHBjSkQr?= =?utf-8?B?M2VWUGpxT2JYSmY4L04rVmdkaDFxZlM1akU4SXJiejk0dUNUMVlkV3JaM0VI?= =?utf-8?B?ck01anJGWW1OTTNTTHFxRVJ0WGh1WVBSdU9wRHJVUUJoTjVoQjBxVWpSb0R0?= =?utf-8?B?eElrVnVrS0pmVkFDRjB6SkFhK01rUStWekVuVTVPQVY3U0VZK0pkZU5xQUFU?= =?utf-8?B?RE0ra25EYVpPN0p5WW96aDF4Ym5GblJpZFBTVXRGQy9KUkRDSStZRmIvWTNO?= =?utf-8?B?SEg2K3J2ZTcvTFZLUGQwMFRoQWNiUGNwZzNZQ0NBVi8xb2RzM1JURFVtelJW?= =?utf-8?B?VTQ4dW9sUnVVdVFzTkErWWFzM0cweUZuZTlYZ2F0M0lLaEJGMXZLQWwrU3hL?= =?utf-8?B?bG5KVVBOd2VRTUUyNzJvZThFSzNVc3lvcnNLRDN4ZzVWbDh1L2x4dkhFNVF1?= =?utf-8?B?UTVwRWhGVFlJZ1pvVmtuSjc0L3lJOTFEMSs2V3djN2lydnEvWjEwWExaYlU0?= =?utf-8?B?WU56S1M2K2paVkFDMDExbkFGWUo4blU0WTh1ZXlRRkZVcDJ5NmVFTXl0MFV0?= =?utf-8?B?eE9LM2duWmNVdk45QW9ncWtxNkQyZ3UwSTBRR1E1RStMTWhqTFA4MlRIVHhk?= =?utf-8?B?L004Z0NCR1JQK3hXblA2cXNtSVZvb0VaaGZyZnliRmJpU3VESkpER21YdHFs?= =?utf-8?B?cC9SNTJXdFBtMEQzRFdpTFBSQ203RzN4aFh0b2xnWG9mNEYvclFQWlp4YkYv?= =?utf-8?B?RlhaaW1EeDUvR01XREdmNzBGQkdTbGRaa2FDYW9RZFUraXdTWEgrRUVTYzVC?= =?utf-8?B?aGlhdmZRWjkvZ2NNNzJoNlBWejFTbElpQjl2NDdtZEcxZHRjY2E1Z2tWL25k?= =?utf-8?B?dTE0QmZFK2xCODIvN2RrYzA4Y2l4WXVWOGJyUFpwRHE3T2cxSVhDWVYrVDVQ?= =?utf-8?B?UnNEM25BYXh4SEpPeUNqdnhldFFOVmpMekZqN2lHL0tVcGlwaDl6NXRDZUFx?= =?utf-8?B?QytPZDkyZ3FxSGE0MVBwQUNIVlhSMWIzOTNRdTkyT0JoRU8ybDhUTkJMZ1Mv?= =?utf-8?B?T2pja0gwc3dvcjhpSWs3dnJ1OXVsd2U0bitIS3FsR205QnF0MW5aTG8zQy80?= =?utf-8?B?Zy9uL01IR2ZhaGh6ZTg4T3Bld21ya2hpWWljRnhrT1lSK09YSFlRNWczZHZv?= =?utf-8?B?M0NDVTR4Unl1Z0ZYYnU3N2lNZkJZSmQzYThCR3VteU8zQThSeTZab1BZZngz?= =?utf-8?B?QTdROHRnS0tTaVlFQ2k1d3d2cGJrUGV1VHpiZXVRV01yL21sZVhkdUlKSFR5?= =?utf-8?B?OWNaS25mbC9hMjNmOUpCTFhtckpaZURLNGVyUjFpSkI3L2VPbmkwRmhyVFAz?= =?utf-8?B?NzVIZXhucmxnVUVHRmh0UnJKK3pWVlJjUHVHRnJsMW9FSU1RaldoUThzV1Mx?= =?utf-8?B?ZHJGSTJ6YUgxNEZqTGhDRHRQNGowWklJemJObGxMd2J3YjNwMURDaDB3T1hD?= =?utf-8?B?RWR3ZExGTXlKU0xEcmtwSkhDY3ovdjJyMk9JRTFLbE9tSlZGM2lQdGh6dmpL?= =?utf-8?B?aXl6SjM1V3QxUnVwNzNkRW9oNWQ3dzB4ZyttTnRWYU9vQWhYVkZOR1lFTUgv?= =?utf-8?B?UFpDeFRPMWMzemtVdkljdHhuTmNmeThqUEJrbmhjSUFKNTFFOHZGR05DTEQ5?= =?utf-8?B?cW1Ya2NNSkcvMzduRmtzL1U0SDc0Y3ZyanRKWkFhQjFVRGFIM0lpbWxxZDJm?= =?utf-8?B?R3JLOXErQTZHZHdCS3dMZGUvTEFyVXNmWElNQTZNUDk2ODhvMXE1dz09?= X-Exchange-RoutingPolicyChecked: dsh96nr9YnqmNSB74UHnKvR3Nd6DsmnZKgcd14zBnDqkKHV6yNWEZSt9Ay4J8jVAYHslmBwTtD/DDl+Sm8w7Iy8ci9ueiPOGSTLxrOnIOQ/zv5b/V0Eh1LRpnox3IGYMK4+1R3CcbCBgak/jsfKrltQhcIZO/wZYgt2RPcCA/ANIZjIc4xKXzbSwnxG386q5Jk5pmaxfYRlb7FosXUZOsL12HLr8cMblfRAOC3x8pTRnUzWgHp4V3rupwCJX/ZRY7RWoES10hrIf2aw3WCPpuZ5CEjcZRKMIPst3gknd/MlgYOACrjHjlaInrloB3rfGuhBBKXjrUInK0NhTDaXq3w== X-MS-Exchange-CrossTenant-Network-Message-Id: 64d65fb4-8828-4bb6-da72-08dea7b5aef6 X-MS-Exchange-CrossTenant-AuthSource: DS0PR11MB7925.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 01 May 2026 19:13:10.1335 (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: KSUluEBzcSC6lqNT+3QWZQGCFAWi5opYO1qBGb+QkmqAhaagJ9lMuIR98YrDu6gGDjIXgcHQ+TGgDShYzr+Zr3hk+3LWYCl7EN7u86wZPRs= X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS7PR11MB6222 X-OriginatorOrg: intel.com On 5/1/2026 11:44 AM, Andrei Vagin wrote: > > I've been thinking about this more, and I believe the claim that XSAVE > offsets can differ across CPUs for the same feature is inaccurate. The > XSAVE standard format uses fixed offsets specifically to allow migration > between different CPU generations. If a feature exists on both the > source and destination CPUs, its data resides at the exact same byte > offset. There is commit ba386777a30b ("x86/elf: Add a new FPU buffer layout info to x86 core files") for this reason: ... The XSAVE layouts of modern AMD and Intel CPUs differ, especially since Memory Protection Keys and the AVX-512 features have been inculcated into the AMD CPUs. Since AMD never adopted (and hence never left room in the XSAVE layout for) the Intel MPX feature, tools like GDB had assumed a fixed XSAVE layout matching that of Intel (based on the XCR0 mask). Hence, core dumps from AMD CPUs didn't match the known size for the XCR0 mask. This resulted in GDB and other tools not being able to access the values of the AVX-512 and PKRU registers on AMD CPUs. ... Thanks, Chang