From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.13]) (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 AFFED3815D4 for ; Tue, 30 Jun 2026 19:23:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=198.175.65.13 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782847432; cv=fail; b=aZk0R6x4sg7CG4lWkt5N3TIT8TC/eGF/m1GMyEZkrKfRGlHajbAOZJopHfQ4Xo4o9jTu84ASDFLvA0/YvVr6nXYeV9kmOmtIuN3UXGq3j2M+ELq+3spVEyaaHhvwHDtJp/7G0pRe3f26PBezlhX2o/LZJ8lEe0b++1lQrTS0po0= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782847432; c=relaxed/simple; bh=BNXb0cOzkz5imtnVyLw9719p3BQRBW2iQtfqsQ3e7Qs=; h=Message-ID:Date:Subject:To:CC:References:From:In-Reply-To: Content-Type:MIME-Version; b=ehrsaJ6UFTWcfH9AxUUC2hcBJ8Zi0JVFQEYDJxHGSZvGFR0CL6+/9V9Hx8PDp3mIf9QcKDd9H0bsBqcRDPiC87AOA8ir6XMku9Dy/aSJHOykbGVhWhbzQ91CHn9aWiNaFUgct9GhZ2PZnwpwHI2PoGIrwtxFxCnj1MgcFoB5/3Q= 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=FiVR/9Qm; arc=fail smtp.client-ip=198.175.65.13 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="FiVR/9Qm" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1782847430; x=1814383430; h=message-id:date:subject:to:cc:references:from: in-reply-to:content-transfer-encoding:mime-version; bh=BNXb0cOzkz5imtnVyLw9719p3BQRBW2iQtfqsQ3e7Qs=; b=FiVR/9QmUcK8pnrRMkBQ1LKnUyVKjlgOhO9dAq/lhlqIs6ikMykwI72a HB9Urts0vyzsg/KOTKMwZUc2q0Rmq4zGNLFxZjmFw8/YaePd3UkZasL/L lqMlkLMDEKHn1Smmy991cLwYhW4E9NH9VUMoYlknO3oWrvudxPKqnXpAx HAzfNQeBIefgIcoh4I8E6wHneTAxj7m4vR8U7QhKAOdqcrfTF4mwLenyD IgsMW6CmjdKp/VsoO8mbNHkv3Jhxgs94H9qiwlNXXtY+MnXViWOzGUHDF ri3tpvThsofToeUnd2AujaLHIq8tDnzloSSLOICt/4GY4v+lN9OxbL1A8 A==; X-CSE-ConnectionGUID: VZi4t6rCSD65WGS45AdSFg== X-CSE-MsgGUID: hbzvDjZKQT6To1zqpIJL8w== X-IronPort-AV: E=McAfee;i="6800,10657,11833"; a="94721853" X-IronPort-AV: E=Sophos;i="6.24,234,1774335600"; d="scan'208";a="94721853" Received: from fmviesa007.fm.intel.com ([10.60.135.147]) by orvoesa105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Jun 2026 12:23:50 -0700 X-CSE-ConnectionGUID: fN8GSXRpTTiEE6H1M0A+5Q== X-CSE-MsgGUID: NMn5/aL/TfKQNOl3rEnvww== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.24,234,1774335600"; d="scan'208";a="248986676" Received: from fmsmsx903.amr.corp.intel.com ([10.18.126.92]) by fmviesa007.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Jun 2026 12:23:50 -0700 Received: from FMSMSX903.amr.corp.intel.com (10.18.126.92) 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 15.2.2562.43; Tue, 30 Jun 2026 12:23:49 -0700 Received: from fmsedg903.ED.cps.intel.com (10.1.192.145) 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 15.2.2562.43 via Frontend Transport; Tue, 30 Jun 2026 12:23:49 -0700 Received: from SJ2PR03CU001.outbound.protection.outlook.com (52.101.43.48) by edgegateway.intel.com (192.55.55.83) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.43; Tue, 30 Jun 2026 12:23:49 -0700 ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=QBxRrsSwIeKBVEd1Rdrs6fAjl3mUsXi1Y1DC9cnh7zacUo4PYE/AszbIzLw1Nhx5ptZJrCo9yRJAZEH+Ixu1fZXN/NBHOUAQEZC61jit8Paz05t/d3sUYVujYAZ9gOtOjLggVp3QzLRkNRvLvf4Q8IVraPsSQtzOR3J0aO7oN+J6gA2nh9eyeZ0UPuytcWafK8WylvBFeJN6+7zk87IZPZ0Mk4HRptOEFWcwbF4budo0A2Ac90WnRU3h8I37/r5LndaJKBRiSrmxx+LalHSe5Dt/1m+PsOdBetSXt8cYYfmvfZipPRCGWz/ZNUmZjPIYBwtVDfoEK0fKQP8phmwVbw== 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=eKTgghScE7IGNV5gJt6uAGwmWYHc43MufJW745zcYr8=; b=fsol8fUwp9G/8yFw7hjU23DVrrl7Fk738u5rzURGPnXQLiiajGrkHt0BRmWWYoYBazLEpYvn0GwJxTAVbkWHpxUgmfpWn6aBcc91kr+o4YgDwGT1cN71oT15IX9QQ1oLUrkUfdIrujn43FoR8Qr/Vytx/JniB5hm9Xx9E6NcKg4wqoZuIoz5Ra43SxBX99LZ6ceXs1aKl6HyVGb18JxA3uOnd+dKmC01uY5F86w8XPBI15wFrLDnQv16GxfaD4XLbS0pc5Sh+NANOQKe62XeWHGZgCxI47Oz1MBFMC41HIjB7l3UT4iAIv61i+0Z7qevTO1eJU0Lo/5lQRHu4KqMuw== 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 PH0PR11MB4886.namprd11.prod.outlook.com (2603:10b6:510:33::22) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.159.16; Tue, 30 Jun 2026 19:23:48 +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 15.21.0159.018; Tue, 30 Jun 2026 19:23:47 +0000 Message-ID: Date: Tue, 30 Jun 2026 12:23:46 -0700 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 04/10] x86/fpu: Document reasoning of FX-only fallback To: Andrei Vagin , Thomas Gleixner , "Ingo Molnar" , Borislav Petkov CC: , , Dave Hansen , , "H. Peter Anvin" References: <20260615193716.1843340-1-avagin@google.com> <20260615193716.1843340-5-avagin@google.com> Content-Language: en-US From: "Chang S. Bae" In-Reply-To: <20260615193716.1843340-5-avagin@google.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BY3PR04CA0006.namprd04.prod.outlook.com (2603:10b6:a03:217::11) 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_|PH0PR11MB4886:EE_ X-MS-Office365-Filtering-Correlation-Id: 63b60161-0aa4-4598-0d62-08ded6dd1bb7 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|23010399003|366016|1800799024|6133799003|4143699003|11063799006|56012099006|18002099003|22082099003; X-Microsoft-Antispam-Message-Info: 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 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)(376014)(23010399003)(366016)(1800799024)(6133799003)(4143699003)(11063799006)(56012099006)(18002099003)(22082099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?M0FMeVZYbjhPYTFLamJrQURSZ1dmMFNGR1BmVyt2M1JBMFFGSDRGMkxKNGYr?= =?utf-8?B?UUxvUUZ6clQyaWo2aTMrWkFScFBqWDZCZTBmNmdrM3NQcmNRcysvd2ZFL1E3?= =?utf-8?B?ZkFYZnczWmJEU0NLU3ZoQnlCSi85S0dVZXNkZm9BTnhxcU5DcTRMK2dlYkNx?= =?utf-8?B?N3JyQmVteVVlU1hLVXpZTmJVejhMTUV4eWNCTmNFQW4wRWNHRGVrQlpaQWpF?= =?utf-8?B?a1hUSXk1amZhaDZpNmpOY0R1dlltak1uNjV0VUd4RmtmK25LTU8yZGY3eVpC?= =?utf-8?B?NHJ0THpHcU1yZGdtR3pIdVVXdjJPYlZlMkJaemZBeHEwc2NUWXdDc3YzbE9B?= =?utf-8?B?bXZZVzROeFVMVVBabTM3WkdEN01sT2tvS0RPZ0tpaUIzMmttUWZDOC83WXhV?= =?utf-8?B?a2lTY0hwWFdnbzhtd2VMUHk3NkRkWE1hVUo2M09nek1MY3hMTnV4WW85aGoy?= =?utf-8?B?d3J3RW9kOFBraFBHNzJ1NHNPUWxFTG5RQlZMb1BlNTFyckt3M1d5UXNQMExI?= =?utf-8?B?THMvdEw2QjlrNVhsWVVCeVFIendIOEJYT2FnMitoamZkZm5pVXVaditsQmhR?= =?utf-8?B?TXFvZG5vdnV1d2ROb0c2MHpjMHlVZ28zeFRod0hlVThqVlpkM3dCZEZuTExm?= =?utf-8?B?Z3BpZFZpcUVzQWdMcE1vR0VzcG9FN1FtbGhJYkNwZGZTbllweVN0TVFWQXRX?= =?utf-8?B?MzlsS2QyYXVwQUhsN3VBTHM4enVwQnpNU3VIcWJkMjFVQ0tiWnRwQkJ3VGwr?= =?utf-8?B?ZVltNVZSaVU4Yk1BZ3NvQThQaEJHdCtuQ3lBKytuUEY5TVMvaWJ0d1BzZnpx?= =?utf-8?B?YnRjSnNFWEZyVThxQmlvTmZKRzQzQ2lseXUwMUZUdlA0b2ZCRXR4R0dhNUd1?= =?utf-8?B?YU5sb1lqcUphdnZ0NUlDV0JkdHo3cFRMK1FYNmlIUmV2alV2b1JscGVySnNX?= =?utf-8?B?Um55MXBLaWVodjVmMm1VNEJWNEdWQjdxUXhsUS9GbGpHdDU2OXdoc3gySmJ3?= =?utf-8?B?QjBoL0tVQXZrZjFjczgyUkV6Z2VZVTlVNCs3M2NhV3Fod2NlMVJTQmVreUEv?= =?utf-8?B?Ynl1Z3dwYVR0S3EwRXFka2JMbUlsUS9OcmlVVnU3NGpDczlVTHo1OGJnOUp6?= =?utf-8?B?QWh3WWZ2S1o4VHhNNThNWTJ1SldPZEJoZTc2aml3K2wvZ1RGVFhQbFEwN3hq?= =?utf-8?B?bmF2K2pSc0hyTE42N1ZiOG5RcmNMU3pjem45VVJHRVhoQU5IbFJhaUZYM25Z?= =?utf-8?B?T2Z5aU9xNGhqWC9iekQ4QUdDLzBYTWxRRk1tc2Q0TEM1ZjhrS2ZNVXQrWU82?= =?utf-8?B?QWRmckUxQmF5NWZQRlRsb2dHbXlqUWorQlZHaVV2VjhRaDhBVmpTaGEybjlE?= =?utf-8?B?T0dsV3BtTVY1TlFCUDlxTEhqRFBEam84SkMwYVFCT3BMY25xYTY2YWd1OWdU?= =?utf-8?B?d0EvMm01NDYxWU9IWGtwUkhMbXkvbkw2dzlIKzBUS3NvYWtOM0tFZ0NzQytM?= =?utf-8?B?cHl2d2F3dERPS3RYUTdpUWxsLzFobTc1aSt5Sm5qNzNvenYxQ29TWk44ZGc1?= =?utf-8?B?UWpBUGZqT2NYb2ZQamJ4NWZnZVpxWC8wZndhWncwTmFTWERpMnNTUkoxQ2J5?= =?utf-8?B?NFJFY3NWUmhtaHpDYWxrc2xWUWVpbktybXJmeWtiWVVBWDBmU0JmUnkrWWhQ?= =?utf-8?B?c0hidUJGOHFnUHFFNk85TXlERUE4Z2FNd3duSThqSWpVNit4S0d1aWdPOVl2?= =?utf-8?B?cnlxWnY0YVJGK1E0MjRqWFhaemo0cXNjRTRJdnJmTmpRSVpKb3hoSy9lZlZU?= =?utf-8?B?MHl0U2dlTzNUSHBRK0E4UUI2MERYM1RQbllBVXhTRWp5TGkwdVNPQUt1RnpN?= =?utf-8?B?R05ubExVdEwrM0N0Nk9BdDNMUnZDOFd4VEw2WE5xM1FBMUVnZU5Fc0x1UEtH?= =?utf-8?B?UWM1WXFxSzgrdTFVcHJWQ1YrMjBCbEpERDVTTHpwSURvUkhtUkNRNjB0SVZS?= =?utf-8?B?N29YTFhYZE02eVphclhOYWxvaG1LMm1GdEQwQmJJdTJPUG9hNWN2RFRCOEc2?= =?utf-8?B?bHRiTVNUbHlUakNJRUFFV3VQdnBtTEVRMi9YTnRGMmU2WHpFZk9iUit1SnI4?= =?utf-8?B?L2F4R0VaZUNGaXhHZUt6TWNxSEt1WExwRDQrZFFhWndCWHdua2dibllKb0hT?= =?utf-8?B?S2NGYzR1NHlCdDVyK1VMTm5OODRIQ25KS2svU3Uya2t0LzFMSjlGMlNLeURy?= =?utf-8?B?dmdKeWlnVGtwVWczdCtQWlppUW1MQlpUcm9LODZTSG1lSHNtT3FRdVQ4OGRq?= =?utf-8?B?K25RdWsvNWJpZnJsemdJU2NHQllLZi9ZMkh3cHJrRkpxbGhkb3RTZz09?= X-Exchange-RoutingPolicyChecked: Gep9CJIHlxzkndQZla0hqpyPnt1A+WJIF8n8S6B/ypoGvmjeqL6qN1UzcaHhTwgSVNf9bfAIA4J/339kTWVU9BayYcWSeGrdfHkey1sJidgzK+rJ4Yk53UBsNkgxL+J/zoFApZUrOvYoXHOKvAxhBCW5R/2QjNnb3pfONHhG3GR82gubD6qhhDS03I4IZAcNemGS07dFnfWuTsZULOF6ZbQV2xSY8RJaZOg+9kOQtBaliVJEpVr+t1r4iybVvAn4Y10P5XrxFJgNBfZUfkIJnpBG/v0mBjUzYu3z2+uF7Vb/Taduox7pt65egJA8GcA+ly0K6wOr53v5Gz2J9ik5Nw== X-MS-Exchange-CrossTenant-Network-Message-Id: 63b60161-0aa4-4598-0d62-08ded6dd1bb7 X-MS-Exchange-CrossTenant-AuthSource: DS0PR11MB7925.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Jun 2026 19:23:47.6017 (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: u8rDYKpEKoRTk8313PcC9oiNKgQnZ+3vMLWf92CK2+nuP3C9F2ArnSgGfd2FqU57tfVhG4i0yVR8rUUXcRRpdbTyDM0Mn3b4YGuDB9zj/FI= X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH0PR11MB4886 X-OriginatorOrg: intel.com On 6/15/2026 12:37 PM, Andrei Vagin wrote: > > This fallback is dangerous as it can trigger silent corruptions of > user-space state by resetting extended registers if the process was > using them but the frame metadata was malformed. > > XSAVE was introduced 15 years ago, we may need to consider removing this > fallback entirely or introducing a sysctl to enable/disable it. This reads more like a separate problem statement. I don't see any follow-up implementing either option here. Without additional context, it isn't entirely clear to me why this should be in this changelog at least. Thanks, Chang