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Fri, 3 Mar 2023 20:58:12 +0000 Received: from PH8PR11MB8107.namprd11.prod.outlook.com ([fe80::421b:865b:f356:7dfc]) by PH8PR11MB8107.namprd11.prod.outlook.com ([fe80::421b:865b:f356:7dfc%5]) with mapi id 15.20.6156.018; Fri, 3 Mar 2023 20:58:12 +0000 Date: Fri, 3 Mar 2023 12:58:10 -0800 From: Dan Williams To: Fan Ni , "alison.schofield@intel.com" , "vishal.l.verma@intel.com" , "ira.weiny@intel.com" , "bwidawsk@kernel.org" , "dan.j.williams@intel.com" , "Jonathan.Cameron@huawei.com" CC: "linux-cxl@vger.kernel.org" , Adam Manzanares , "dave@stgolabs.net" , "linux-kernel@vger.kernel.org" , Fan Ni Subject: RE: [PATCH] cxl/hdm: Fix hdm decoder init by adding COMMIT field check Message-ID: <64025f6219d2d_71138294e5@dwillia2-xfh.jf.intel.com.notmuch> References: <20230228224014.1402545-1-fan.ni@samsung.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20230228224014.1402545-1-fan.ni@samsung.com> X-ClientProxiedBy: BY5PR17CA0061.namprd17.prod.outlook.com (2603:10b6:a03:167::38) To PH8PR11MB8107.namprd11.prod.outlook.com (2603:10b6:510:256::6) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH8PR11MB8107:EE_|CY5PR11MB6368:EE_ X-MS-Office365-Filtering-Correlation-Id: 88853d88-1f76-4d30-40e7-08db1c2a0060 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; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?R6zhciBasSZJEckrh8bsnPnQjsNqDyJN80mW3wyt9MIcUUtIIEjHbmtUGDLh?= =?us-ascii?Q?MQPvQ/RqknCRUcTLU2Ee5bifFE3BkszldO+KxVHcnc5yc6QLRaYtgyjOAnpR?= =?us-ascii?Q?FuaNGM3idRf+4zI983Gc4hYfMoHfHUHb3Xd0KtZmIBerheHGMiGI0f9FDEmc?= =?us-ascii?Q?FZ0B1E2MM2fPCtzM9pBXPgM2f8SmTGZdfX+LJd/YUgeaLarKZBkSKCIO0oUI?= =?us-ascii?Q?cuyzX2hEx6vMhtk8ADPM3AgbSXvnQNGhHH09+G6lSHpzR2b3rjvMFfzXASAt?= =?us-ascii?Q?+xqvnJgylm45i1Ch9xA/v+RUz+ZAZn2rp3mi3goWL2Bzh+co3lcP+zbl0u88?= =?us-ascii?Q?miHgyfkmJ4qkoC0/Q3xSsv4iIj0jWdn2xLjy5Tixg8X/3Q6lCvoExjLqM0xy?= =?us-ascii?Q?wgp5F6CUKiGTwV75LhVw8qweAjHZI2vA7nfsynUHgYnpJqEPsWt+xoV4p/eo?= =?us-ascii?Q?dlSubIFCNW3FyVy/OLh7W/G+xApCaDw0bS3WJbQtEWeMGcHR8znzjRZCRf2O?= =?us-ascii?Q?k1f/o8xOrBgjQ/GFetKM1G8Ptzzp0f9d+9Owy2RGlIwoySo4eriMotuGBash?= =?us-ascii?Q?Ish7/b5R39oPBAnNG4OZK8apG4sj+fsmXPvPi56E5RHanR7tN1V+8AEbR9Jx?= =?us-ascii?Q?jjHgVE3sEnMxJkMrxtG/kLtBi5zugfAJBfBQwVkswtbbAshNl6+X0ZswS7qa?= =?us-ascii?Q?0dX1ZL/BBps8LvAx7BTfYEUFRKEOpXVbLF/OMQHIJl4D058CMeZV/4MkMTr6?= =?us-ascii?Q?5aBfO9+eGBUVbBQajQFNNl/qoheEK1AdItsqeU7PSV3jblIuYg1Zv0mOV4ft?= =?us-ascii?Q?re7pSRZLqnElZP+Ywiydkce+VWVVgzmpCmS5ky5atZLg8yKX8zR4pQJwuJoc?= =?us-ascii?Q?gWc76T1iB4VTZRZWuReQe6SEDut6hK7VcFRpbptxD59yml/xfMupha0LddWB?= =?us-ascii?Q?KoJ3yFQTRP17oTKJUq53SklXEpsj8Spqavij2vJIrDeDBlwxiAgh5M+IGs28?= =?us-ascii?Q?pisp5j3ajzCC2FeZVEc/CHcO5RuO8rNHMxKFMRjGwmUQu/qDy1IAZMWcADxX?= =?us-ascii?Q?lfwFXP+QKNWjIesHSLwbP33Cbxm76uyuWGeI5Hkwe3t8OpOslQ+BEf48TSpg?= =?us-ascii?Q?tc0iWnQe19KcN+8HfIP8Xc00vZCPqg2HiiecXDUyfcNg/JC5m1OONZ0pguYO?= =?us-ascii?Q?CtHbLc7Szb9/FAI/DazBuSajH/odf1GPkQHxB+GdV2B6g+HA6nKjbEoLXYER?= =?us-ascii?Q?1w3xH8hI8Xs/yy/8stJ03iySv+gwQN+rx7xsgl3K0lWNW386XFCfpMAl4uDv?= =?us-ascii?Q?hl+SRL3zfFP9/aoUnLJRIVnMfuOsS4Q+IjvO195l0IcaLWDuzGPlh+NtAedu?= =?us-ascii?Q?o2DwjHxYE4MTt1XsLUiRzw/ATvqznjV/UuAPbpI0g7NvI17+BiBdc9tKzBmP?= =?us-ascii?Q?fRIAMwAwI9cght1cYfVRdCY3AN5I0rFnakFawcUR6ufbHuLpG9RAFKc3gWXH?= =?us-ascii?Q?F1wyaFcYfRjYsPL473D+M9S8iHX1FVYFOjo5FgwSjAuAETQVRdc6Ii/nyFPJ?= =?us-ascii?Q?NpU2QAYL+atd3C43mgLXrQCHJrlQzz6p2/j9zxS9/cDy1WPsmrII5L8pu5t1?= =?us-ascii?Q?1A=3D=3D?= X-MS-Exchange-CrossTenant-Network-Message-Id: 88853d88-1f76-4d30-40e7-08db1c2a0060 X-MS-Exchange-CrossTenant-AuthSource: PH8PR11MB8107.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 Mar 2023 20:58:12.5444 (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: WESLp7bhSwyDAxKkSzHtCIdctYP5H0dgctTZsYYcYLcC2/lrzRarKpI2gJbAHYDg//CeaGrxslIULPhibVZq2DEKW8cE5oOJXKvUPD60b9M= X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY5PR11MB6368 X-OriginatorOrg: intel.com Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Fan Ni wrote: > Add COMMIT field check aside with existing COMMITTED field check during > hdm decoder initialization to avoid a system crash during module removal > after destroying a region which leaves the COMMIT field being reset while > the COMMITTED field still being set. > > In current kernel implementation, when destroying a region (cxl > destroy-region),the decoders associated to the region will be reset > as that in cxl_decoder_reset, where the COMMIT field will be reset. > However, resetting COMMIT field will not automatically reset the > COMMITTED field, causing a situation where COMMIT is reset (0) while > COMMITTED is set (1) after the region is destroyed. Later, when > init_hdm_decoder is called (during modprobe), current code only check > the COMMITTED to decide whether the decoder is enabled or not. Since > the COMMITTED will be 1 and the code treats the decoder as enabled, > which will cause unexpected behaviour. > > Before the fix, a system crash was observed when performing following > steps: > 1. modprobe -a cxl_acpi cxl_core cxl_pci cxl_port cxl_mem > 2. cxl create-region -m -d decoder0.0 -w 1 mem0 -s 256M > 3. cxl destroy-region region0 -f > 4. rmmod cxl_acpi cxl_pci cxl_port cxl_mem cxl_pmem cxl_core > 5. modprobe -a cxl_acpi cxl_core cxl_pci cxl_port cxl_mem (showing > "no CXL window for range 0x0:0xffffffffffffffff" error message) > 6. rmmod cxl_acpi cxl_pci cxl_port cxl_mem cxl_pmem cxl_core (kernel > crash at cxl_dpa_release due to dpa_res has been freed when destroying > the region). I think a separate fix for that crash is needed, can you send the backtrace? I.e. I worry that crash can be triggered by other means. > > The patch fixed the above issue, and is tested based on follow patch series: > > [PATCH 00/18] CXL RAM and the 'Soft Reserved' => 'System RAM' default > Message-ID: 167601992097.1924368.18291887895351917895.stgit@dwillia2-xfh.jf.intel.com > > Signed-off-by: Fan Ni > --- > drivers/cxl/core/hdm.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c > index 80eccae6ba9e..6cf854c949f0 100644 > --- a/drivers/cxl/core/hdm.c > +++ b/drivers/cxl/core/hdm.c > @@ -695,6 +695,7 @@ static int init_hdm_decoder(struct cxl_port *port, struct cxl_decoder *cxld, > struct cxl_endpoint_decoder *cxled = NULL; > u64 size, base, skip, dpa_size; > bool committed; > + bool should_commit; > u32 remainder; > int i, rc; > u32 ctrl; > @@ -710,10 +711,11 @@ static int init_hdm_decoder(struct cxl_port *port, struct cxl_decoder *cxld, > base = ioread64_hi_lo(hdm + CXL_HDM_DECODER0_BASE_LOW_OFFSET(which)); > size = ioread64_hi_lo(hdm + CXL_HDM_DECODER0_SIZE_LOW_OFFSET(which)); > committed = !!(ctrl & CXL_HDM_DECODER0_CTRL_COMMITTED); > + should_commit = !!(ctrl & CXL_HDM_DECODER0_CTRL_COMMIT); This change looks like a good idea in general given the ambiguity of 'committed'. However just combine the two checks into the @committed variable with something like this: commit_mask = CXL_HDM_DECODER0_CTRL_COMMITTED|CXL_HDM_DECODER0_CTRL_COMMIT; committed = (ctrl & commit_mask) == commit_mask;