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Wysocki" , Len Brown , Pavel Machek , Li Ming , Jeff Johnson , "Ying Huang" , Yao Xingtao , Peter Zijlstra , Greg Kroah-Hartman , Nathan Fontenot , Terry Bowman , Robert Richter , Benjamin Cheatham , Zhijian Li , Borislav Petkov , Smita Koralahalli , Tomasz Wolski Message-ID: <697acf78acf70_3095100c@dwillia2-mobl4.notmuch> In-Reply-To: <697a9d46b147e_309510027@dwillia2-mobl4.notmuch> References: <20260122045543.218194-1-Smita.KoralahalliChannabasappa@amd.com> <20260122045543.218194-7-Smita.KoralahalliChannabasappa@amd.com> <697a9d46b147e_309510027@dwillia2-mobl4.notmuch> Subject: Re: [PATCH v5 6/7] dax/hmem, cxl: Defer and resolve ownership of Soft Reserved memory ranges Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: BYAPR05CA0063.namprd05.prod.outlook.com (2603:10b6:a03:74::40) To PH8PR11MB8107.namprd11.prod.outlook.com (2603:10b6:510:256::6) 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: PH8PR11MB8107:EE_|SJ2PR11MB7504:EE_ X-MS-Office365-Filtering-Correlation-Id: 0991a23e-95fb-44cc-5ba1-08de5ee3db3a X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|1800799024|376014|7416014|7053199007; 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Either CXL fully claims the Soft > > Reserved ranges or it relinquishes it entirely. > > > > Co-developed-by: Dan Williams > > Signed-off-by: Dan Williams > > Signed-off-by: Smita Koralahalli > > --- > > drivers/cxl/core/region.c | 25 ++++++++++++ > > drivers/cxl/cxl.h | 2 + > > drivers/dax/cxl.c | 9 +++++ > > drivers/dax/hmem/hmem.c | 81 ++++++++++++++++++++++++++++++++++++++- > > 4 files changed, 115 insertions(+), 2 deletions(-) > > [..] > > diff --git a/drivers/dax/cxl.c b/drivers/dax/cxl.c > > index 13cd94d32ff7..b7e90d6dd888 100644 > > --- a/drivers/dax/cxl.c > > +++ b/drivers/dax/cxl.c > > @@ -14,6 +14,15 @@ static int cxl_dax_region_probe(struct device *dev) > > struct dax_region *dax_region; > > struct dev_dax_data data; > > > > + switch (dax_cxl_mode) { > > + case DAX_CXL_MODE_DEFER: > > + return -EPROBE_DEFER; > > So, I think this causes a mess because now you have 2 workqueues (driver > core defer-queue and hmem work) competing to disposition this device. > What this seems to want is to only run in the post "soft reserve > dispositioned" world. Something like (untested!) > > diff --git a/drivers/dax/cxl.c b/drivers/dax/cxl.c > index 13cd94d32ff7..1162495eb317 100644 > --- a/drivers/dax/cxl.c > +++ b/drivers/dax/cxl.c > @@ -14,6 +14,9 @@ static int cxl_dax_region_probe(struct device *dev) > struct dax_region *dax_region; > struct dev_dax_data data; > > + /* Make sure that dax_cxl_mode is stable, only runs once at boot */ > + flush_hmem_work(); > + It occurs to me that this likely insta-hangs because wait_for_device_probe() waits forever for itself to flush. So it may need to be a scheme where the cxl_dax_region_driver registration does something like this (untested!): diff --git a/drivers/dax/cxl.c b/drivers/dax/cxl.c index 13cd94d32ff7..6a1a38b4f64b 100644 --- a/drivers/dax/cxl.c +++ b/drivers/dax/cxl.c @@ -41,7 +41,32 @@ static struct cxl_driver cxl_dax_region_driver = { }, }; -module_cxl_driver(cxl_dax_region_driver); +static void cxl_dax_region_driver_register(struct work_struct *work) +{ + flush_hmem_work(); + cxl_driver_register(&cxl_dax_region_driver); +} + +static DECLARE_WORK(cxl_dax_region_driver_work, cxl_dax_region_driver_register); + +static int __init cxl_dax_region_init(void) +{ + /* + * Need to resolve a race with dax_hmem wanting to drive regions + * instead of CXL + */ + queue_work(system_long_wq, &cxl_dax_region_driver_work); + return 0; +} +module_init(cxl_dax_region_init); + +static void __exit cxl_dax_region_exit(void) +{ + flush_work(&cxl_dax_region_driver_work); + cxl_driver_unregister(&cxl_dax_region_driver); +} +module_exit(cxl_dax_region_exit); + MODULE_ALIAS_CXL(CXL_DEVICE_DAX_REGION); MODULE_DESCRIPTION("CXL DAX: direct access to CXL regions"); MODULE_LICENSE("GPL");