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Peter Anvin" , Mario Limonciello , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] x86/CPU/AMD: Prevent reset reasons from being retained among boots Message-ID: <20251013153440.GA78919@yaz-khff2.amd.com> References: <20251010165959.49737-1-i@rong.moe> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251010165959.49737-1-i@rong.moe> X-ClientProxiedBy: BN9PR03CA0626.namprd03.prod.outlook.com (2603:10b6:408:106::31) To DM4PR12MB6373.namprd12.prod.outlook.com (2603:10b6:8:a4::7) 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: DM4PR12MB6373:EE_|LV3PR12MB9329:EE_ X-MS-Office365-Filtering-Correlation-Id: faf79389-383b-402e-6e39-08de0a6e0b5c X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|366016|1800799024|7053199007; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?qwhS06N4jjO7Mwn/Shk3YIN9RHwNbeBAWPwTQXk8LWv7QVlR6GxU8b/jitnW?= =?us-ascii?Q?GJwn0JELRBXt5+g5nqEqrKFeEaLvfBXhmcy7Fbui+kVwmEKe/pv2jCN/pH+M?= =?us-ascii?Q?RCxRmqkEsY7WaMr8/knNyzyk8l0WW/UddyV6sG7UQt0DsuSCJcbQZVHDnHN5?= =?us-ascii?Q?T5c2K2FmN/qR9jYUB4xzhdJGTSjUPEKlZxLi6rJOdolDmm0y5doH2OXrkgRg?= =?us-ascii?Q?dRCSZhh9kvFjRLh6lbPgS0qAyiP4VcUAnzltAFZ7xPXhlvGgW+bFqKMEyI2i?= =?us-ascii?Q?AukH/IkQ9GgSfGykY986T/stD0YoP4sIS7OM0Utq2NSjQVt4aRKuYKQJUlbL?= =?us-ascii?Q?NVKYgVIzNcPla659Hx2vap7y1TliGHJySCCrLo3UlYuTocpiRkEnnJrqo49N?= =?us-ascii?Q?8QwJCzvqQZKhPpuIuS6v5YW78RsF2LF6D3BduiuO1zcQeijrjLd10tihUbBE?= =?us-ascii?Q?chneFCmQ0KTpW/J6kc8f6k/Ds+ZyWpJUqNL7YJesVFBt1Ic/tz1V95Usv4NY?= =?us-ascii?Q?u8/Jt/6ZUSPYPD4QbEh943vyAjmefBQ72BFJHNRVP5P8FSvXYRJ9TCO6XntA?= =?us-ascii?Q?SNpHhWmELiqqRB040naTPpO81Br/Yn8LV010Uw7Mu/5ICh0TrdS/QjIliv54?= =?us-ascii?Q?hTE8cGn+L6BNqp0rd5VuHa+MnKxZjD5brw1V1vxKaH2+IeH1VlsKFUyE4e+l?= =?us-ascii?Q?AXvsLSWbvKxcI16Q4E374/5yv9rEXrjGNG2t/+vuoCgMg8U5FU92CMyR54Qq?= =?us-ascii?Q?SS6GmDr8qlC7hqIc/jFDsUmvrSIwCfwgDBsBTCRKfFhCG+FJTL0RLB+CSmvQ?= =?us-ascii?Q?MjHRT5ZscZmBI2gG0wtwg1Y0C+3lAc9Eyio42BLjL0knKYXxNgXAFGP1UJvO?= =?us-ascii?Q?jrBjyR1Scy8r/5hKfdVAp0xCqYzI8TsXVH69B80p6+il0o5avAhHDE3/af1a?= =?us-ascii?Q?bMs2/+G/4Dc8QInbcbCb82DfgLl6EYfEXgDWFlMxVLJhW8If7LUtealnVJOz?= =?us-ascii?Q?dhJyIi+k/AbQVVscl9OreEBOWMgFCaZ1PUg9O9eV+CQnIjU8agzpnOWtGVO4?= =?us-ascii?Q?0gmVyUXM2PvCHc42JIewrDs9kFuntKVVXQ4WJPY2MYYR1Bs4xTU67+Zs8jri?= =?us-ascii?Q?Bv7EeoXLuvIIy4ALRhfVNRxNh3LnXFKbYVUmuTxXOTz0+OfW5LRKKRMmOfiY?= =?us-ascii?Q?7piFKzkjLuib5ZTMdFsQ8d7Bsl0KzA6G9dTttDDaPrY+T82AXLKwc7/8iaYc?= =?us-ascii?Q?Xr8YdLvYZ2IZL2bZh1k9oQkSXAnNaoO2mRJ7waQ3kDRSxw/fC1GB7dIUGpak?= =?us-ascii?Q?BmPPtrVMuFmL24EC071aBjpolggkJcFejrhR9queRz3fNuQuWx4X6wczLamU?= =?us-ascii?Q?J0nqOV694VJex3gSozvjUfxaQKCw1KuBWfQjypaceeiIFVfEyYOpUMNPss5u?= =?us-ascii?Q?Fzoh72pzBRL45PAYZ708X3TYI0kE31ELOFwp2F3M25EpdF1Wu53gFw=3D=3D?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DM4PR12MB6373.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(376014)(366016)(1800799024)(7053199007);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?QtzQ19JjD5xtECY+FbVDBu45csqxrROhDi53JUA0YeNfuuNgGR6IBZo0a/y+?= =?us-ascii?Q?AdjWSVr5loMEPxNluquAsuhiF0iGg2ArIzd4xwRo/L7JyTVd3AOUtA7Gonf0?= =?us-ascii?Q?CXUUcBGN8XF6l+WQ8nyI6lLhRVf1RSmmVylIjfCh3rHmcabuSOoJG1GDvPJn?= =?us-ascii?Q?tjnH7NaHk1cz+eo5yghhQ04Wr1TbXpGLaNfJmmbEEhLAwyxnWRF3fug+PfRp?= =?us-ascii?Q?aQa7oXilCxgmirpux0ArnpzJE0Kyc0vXsmAJc22ViTkcK8RWzVh5SAwFi7PX?= =?us-ascii?Q?f2imjiJFK9zVF/xgdWtDAEqsx9ExUgBFkjBZVihN9GmIay94YjxKb5ESylqv?= =?us-ascii?Q?3gIkdYqb3eI6ygBmEsFrt8xtYNuOtf2Vf35dv/Y+Ku6F7EUGc5HXzIQEgO2Y?= =?us-ascii?Q?1RmcabUh4Dq+pj0N9PyXDrCIOOYLRsnNvcSqIF+BT9yaPqoim1/nsYwghJDk?= =?us-ascii?Q?c2IpUT7TV8xInsCfoe6hVq+BIYh+xGz8cvmhSkavD0HMRS3oj1aRHaqJ9evx?= =?us-ascii?Q?ZfyIXOZDE2UvvK5uLhPDb7t1z5B3yBB6D6jPTAITtcmMe1lBY4YOK20Zp2mX?= =?us-ascii?Q?PLfKz8SYD2Gh5I55/6EBoZ07+yAePjUJuDvE2MgxD0bDXD5iy43D4wXhFb9r?= =?us-ascii?Q?d4rKOr20PyBSAX9caV5HkhuRBEcMyMevYu62CoH3f1KV4yHsAX2rT9GPHvKU?= =?us-ascii?Q?XICIk2pcDbOuyxco1GqWoudNUw9lIU8d96QO26QsPK4gvAlMjO16E8rkfl9F?= =?us-ascii?Q?Eo2HBWsj5mlTDjg8JM/Wk4K4VZRIL/WQQT0X1tHGJA/rfL6PaUlgb9tGP5ym?= =?us-ascii?Q?ET/Pffz6uawaXSx8WYhZvFK/2hpzQT4H2IOqGnqs0krKKpfw7Lgsd5mWn9Wy?= =?us-ascii?Q?/NL1a/TNGj90EeQNl9RA27e8H82u1HGl75Z8p2gUYhWJiPAySn+aRfRi+N0Z?= =?us-ascii?Q?lfmPfzLZ88HwQP190LNpoJaQ+rh03vadj/tWr3OuIu9UY9zFAwWSjqOnIJ5o?= =?us-ascii?Q?JGN8evMXDyxdLIBFul9LxwCVK5CjIBS7IzUqZ4yieXm04Qedb4i9wtLcwOrg?= =?us-ascii?Q?0ot+HyJJCLUCx4sL6+IBgcj39s1LO5acBZ9Ur0GQEvl24K3zjRfdOhKBn7SP?= =?us-ascii?Q?+S0jtbTqpOwwQlNwUGu7pWBeXXO0v3iqFE+dmXkGFp2ifbAbG1YzmHpMdbcx?= =?us-ascii?Q?nxDnYqti2vX00fFZbsCi9XxhnrKIg+FhXjx23RNrO4oz8RbJ80fOsILo16PB?= =?us-ascii?Q?SvsVHNHKjQ24Z4I0i2mhLtw9aKe6wiIwQ/RxEYnwCdnrnVHC3g+jacL4IWKX?= =?us-ascii?Q?7v8LmRl2FzPJhhYLCBXj6bRQbq0ZU2WakNx43gaYVGJwh1oWxyOxRiO9IRxg?= =?us-ascii?Q?5OKc3eyqeo7UmnLeUEgLqmBYODq/K81eZqf/ltDkR+Qm7qugggL1cdfd8t4J?= =?us-ascii?Q?tKTBzICHT44uEuccUS0nmSljrSE5EJUY0m0wkskRvk6H7d8GnUb79e2HzS01?= =?us-ascii?Q?RLXQUqvWy+MOkw5ZUWx7IFtqQLiA73Y78kreMN2Oar9Rvok46JlOhYwnpsOT?= =?us-ascii?Q?T1OZFwKlsIFas56WqQd/dYOIuSP84JGmKz56devw?= X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-Network-Message-Id: faf79389-383b-402e-6e39-08de0a6e0b5c X-MS-Exchange-CrossTenant-AuthSource: DM4PR12MB6373.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Oct 2025 15:34:48.9286 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 3YbbjANqGcTvTxPGO7ozwu0+q0a1MAt2w14LimCBOsU/9jzL/bospwTbUJQZdpxhhzi+X7hTUNsgTNRe5hc4Ww== X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV3PR12MB9329 On Sat, Oct 11, 2025 at 12:59:58AM +0800, Rong Zhang wrote: > The S5_RESET_STATUS register is parsed on boot and printed to kmsg. > However, this could sometimes be misleading and lead to users wasting a > lot of time on meaningless debugging for two reasons: > > * Some bits are never cleared by hardware. It's the software's > responsibility to clear them as per the Processor Programming Reference > (see Link:). > > * Some rare hardware-initiated platform resets do not update the > register at all. > > In both cases, a previous reboot could leave its trace in the register, > resulting in users seeing unrelated reboot reasons while debugging > random reboots afterward. > > Clearing all reason bits solves the issue. Since all reason bits are > write-1-to-clear and we must preserve all other bits, this is done by > writing the read value back to the register. > > Fixes: ab8131028710 ("x86/CPU/AMD: Print the reason for the last reset") > Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537#attach_303991 > Signed-off-by: Rong Zhang > --- Reviewed-by: Yazen Ghannam Thanks, Yazen