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Wed, 22 Jan 2025 14:11:24 +0000 Date: Wed, 22 Jan 2025 08:11:20 -0600 From: Ira Weiny To: Dan Williams , CC: , Subject: Re: [PATCH v2 1/5] cxl: Remove the CXL_DECODER_MIXED mistake Message-ID: <6790fc88b4b09_1eafc29451@iweiny-mobl.notmuch> References: <173753635014.3849855.17902348420186052714.stgit@dwillia2-xfh.jf.intel.com> <173753635601.3849855.5582594127330525596.stgit@dwillia2-xfh.jf.intel.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <173753635601.3849855.5582594127330525596.stgit@dwillia2-xfh.jf.intel.com> X-ClientProxiedBy: MW4PR03CA0345.namprd03.prod.outlook.com (2603:10b6:303:dc::20) To SA1PR11MB6733.namprd11.prod.outlook.com (2603:10b6:806:25c::17) Precedence: bulk X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SA1PR11MB6733:EE_|PH8PR11MB7991:EE_ X-MS-Office365-Filtering-Correlation-Id: ac550647-6bea-401b-faee-08dd3aeea73c X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|366016; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?NbpfUcjjiXtGaBz2PiQX8W6We7/sOGEMTjBXgA+AGRkzstcD9sc53yIMkFAK?= =?us-ascii?Q?9FH0a8tR80I979XBOGjIQo3ns4wkOZAaHJkPUsOSJBoTh/+ngU9788ni1cFb?= =?us-ascii?Q?enfMss0gXvP5xqTMhn/tZAWSdyob9nE+hRvFiincyMc0lOHGTTjzq2pSyvaB?= =?us-ascii?Q?fHip0ltzWgtOTxrhoUaTQdlu90GITpIOTAE5Ebs68qUwwoQ5QNO1Vu+2YDlE?= =?us-ascii?Q?hAY6WIEs7CDpPwywkKzH5Ciex4aYxVYYMpv9LSF9flSGcJr/KrnFq54Q02vK?= =?us-ascii?Q?AT4OG7tY5aqifzg/Rl67uzG/5ffgJBcermeJHcUmW26tCJhYycYv79F3mK7G?= =?us-ascii?Q?mcKn/K2IozH6QxRbSfG96l55sDeQBDgwzKo0X7pqGXlk5arnrPz59/mUcwFB?= =?us-ascii?Q?4MBnX3PQvUJ3bIsjfSvv8JzH2r8p6YoplrLZiaMHbKLboZwDQjdF3Xib3u1c?= =?us-ascii?Q?mRFj2ne0jUpoyLxsKQOzhgPFAsYlMKM6Df+Eeq/IPurfh7dNSJdKVNMcK1iS?= =?us-ascii?Q?d6y/TxntXQPmlw+aPvhq+n0wMV/vAPB4d5ItRfk6PekRjdjKJ9PNkbD1plyx?= =?us-ascii?Q?BASA31iLv6qzew/jYx3TwiifBPUyuUUOMM4Rpa+0Re5rh2eCSpp4j1PupLi/?= =?us-ascii?Q?hvGyady8P6anpRVhx+TAGkcfLkeSUSywFJOxFofOateC9QkZ0p6cIud4uSZ7?= =?us-ascii?Q?7XLfwxWcmMjhORf15rruJeEJA18gDPlQsWBC/4FpFqtGeqe5XVlciBDe6N/F?= =?us-ascii?Q?rYsLr5L9zMb8dyZUqbd3k2ALJ4k3VyagjjndKWi1v/53IXsSFilWNHfrvfGS?= =?us-ascii?Q?KY3hGmifVMn6UYh140vvmi8RKeV31p+rnj/tSCPcxULrWbC4ksoisp+7ExlO?= =?us-ascii?Q?+phDWQ0y2astBsvaYpk5dWHE9gZhnwIkV76GZuFLrEAtWax8QJK+1roWoQLS?= =?us-ascii?Q?P4bVcT/v7IOM7yyRdWeTFoLB7BVHssLJxHKLrWPaloJ8aADtcaSZQgjgCoJ2?= =?us-ascii?Q?74mhG0+gQz/ut/pmN1ZZBurYyKDmScJOs91kqFjt9fuRHUZoas9lA+XoiVMY?= =?us-ascii?Q?MPXmtBq7JXzKBkAmbsQTKS1OH2vmW2X91NRbBLyyowXGXkumBjOvA48tOxvv?= =?us-ascii?Q?mCLlueetUiGwjIxatCPT9mLbwxoR52OR0v0vS0uSMw8+0gDQN4GDKK9Vw820?= =?us-ascii?Q?pAuK3CkbA2EMyKGbiUNRCCujV8TWf1QqFNaA6ajOwqx0m6B2tfUNblYBJvR0?= =?us-ascii?Q?7Jonkef0qg0IBjTgdFZizqMDeHstEOGWORVauOVFMk1MZhQ7vV2W+WXflnh9?= =?us-ascii?Q?NPMhcaIs2Pd9RbAdENNzsLDSkmuh6xh0PsN+1l33xBzOW3dnA1V0ZUqMlZcb?= =?us-ascii?Q?e0fGa8FbkUoqb9EnVk3u+WrNXK7JifGH5Ly6ZvVX6q2+1eHUY37ca0l7FUqH?= =?us-ascii?Q?fiqthU0oGyujrPivmlP7SaRJ+Br0sZd9Ig47IjNwQg2+etrtomRT6kJbbOzS?= =?us-ascii?Q?AnKEhaPr6XeP4S8bTefs9YSK/6vff9nz+rtSI04KWguZ7Nj4xzFHFzw3EL/l?= =?us-ascii?Q?9mQcdF9/pDxLIKwjfBdGigBYOngZaO8bKx51yGbj?= X-MS-Exchange-CrossTenant-Network-Message-Id: ac550647-6bea-401b-faee-08dd3aeea73c X-MS-Exchange-CrossTenant-AuthSource: SA1PR11MB6733.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 22 Jan 2025 14:11:24.0809 (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: iYKNTGU/nxk1v4tajHUKKqMcVFd2zsF3etlJaH1/Rcz3FUXzTwl7diDQXye6kpKqPqc3UBeu4tR32pYPEA9bTA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH8PR11MB7991 X-OriginatorOrg: intel.com Dan Williams wrote: > CXL_DECODER_MIXED is a safety mechanism introduced for the case where > platform firmware has programmed an endpoint decoder that straddles a > DPA partition boundary. While the kernel is careful to only allocate DPA > capacity within a single partition there is no guarantee that platform > firmware, or anything that touched the device before the current kernel, > gets that right. > > However, __cxl_dpa_reserve() will never get to the CXL_DECODER_MIXED > designation because of the way it tracks partition boundaries. A > request_resource() that spans ->ram_res and ->pmem_res fails with the > following signature: > > __cxl_dpa_reserve: cxl_port endpoint15: decoder15.0: failed to reserve allocation > > CXL_DECODER_MIXED is dead defensive programming after the driver has > already given up on the device. It has never offered any protection in > practice, just delete it. > > Signed-off-by: Dan Williams Reviewed-by: Ira Weiny