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Mon, 23 Mar 2026 19:54:55 +0000 From: Dan Williams Date: Mon, 23 Mar 2026 12:54:52 -0700 To: Smita Koralahalli , , , , , CC: Ard Biesheuvel , Alison Schofield , Vishal Verma , "Ira Weiny" , Dan Williams , Jonathan Cameron , Yazen Ghannam , Dave Jiang , Davidlohr Bueso , Matthew Wilcox , Jan Kara , "Rafael J . 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: <69c19a8c66fd3_7ee3100e3@dwillia2-mobl4.notmuch> In-Reply-To: <20260322195343.206900-4-Smita.KoralahalliChannabasappa@amd.com> References: <20260322195343.206900-1-Smita.KoralahalliChannabasappa@amd.com> <20260322195343.206900-4-Smita.KoralahalliChannabasappa@amd.com> Subject: Re: [PATCH v8 3/9] dax/hmem: Request cxl_acpi and cxl_pci before walking Soft Reserved ranges Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: MW4PR03CA0262.namprd03.prod.outlook.com (2603:10b6:303:b4::27) To PH8PR11MB8107.namprd11.prod.outlook.com (2603:10b6:510:256::6) Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH8PR11MB8107:EE_|BL3PR11MB6459:EE_ X-MS-Office365-Filtering-Correlation-Id: 0536b232-6a99-434b-b6d9-08de89160e1c X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|376014|7416014|1800799024|56012099003|22082099003|7053199007|18002099003; 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MODULE_SOFTDEP() only guarantees eventual > loading, it does not enforce that the dependency has finished init > before the current module runs. This can cause HMEM to start before > cxl_acpi has populated the resource tree, breaking detection of overlaps > between Soft Reserved and CXL Windows. > > Also, request cxl_pci before HMEM walks Soft Reserved ranges. Unlike > cxl_acpi, cxl_pci attach is asynchronous and creates dependent devices > that trigger further module loads. Asynchronous probe flushing > (wait_for_device_probe()) is added later in the series in a deferred > context before HMEM makes ownership decisions for Soft Reserved ranges. > > Add an additional explicit Kconfig ordering so that CXL_ACPI and CXL_PCI > must be initialized before DEV_DAX_HMEM. This prevents HMEM from consuming > Soft Reserved ranges before CXL drivers have had a chance to claim them. > > Signed-off-by: Dan Williams > Signed-off-by: Smita Koralahalli > Reviewed-by: Dave Jiang > Reviewed-by: Jonathan Cameron > Reviewed-by: Alison Schofield > --- > drivers/dax/Kconfig | 2 ++ > drivers/dax/hmem/hmem.c | 17 ++++++++++------- > 2 files changed, 12 insertions(+), 7 deletions(-) > > diff --git a/drivers/dax/Kconfig b/drivers/dax/Kconfig > index d656e4c0eb84..3683bb3f2311 100644 > --- a/drivers/dax/Kconfig > +++ b/drivers/dax/Kconfig > @@ -48,6 +48,8 @@ config DEV_DAX_CXL > tristate "CXL DAX: direct access to CXL RAM regions" > depends on CXL_BUS && CXL_REGION && DEV_DAX > default CXL_REGION && DEV_DAX > + depends on CXL_ACPI >= DEV_DAX_HMEM > + depends on CXL_PCI >= DEV_DAX_HMEM As I learned from Keith's recent CXL_PMEM dependency fix for CXL_ACPI [1], this wants to be: depends on DEV_DAX_HMEM || !DEV_DAX_HMEM depends on CXL_ACPI || !CXL_ACPI depends on CXL_PCI || !CXL_PCI ...to make sure that DEV_DAX_CXL can never be built-in unless all of its dependencies are built-in. [1]: http://lore.kernel.org/69aa341fcf526_6423c1002c@dwillia2-mobl4.notmuch At this point I am wondering if all of the feedback I have for this series should just be incremental fixes. I also want to have a canned unit test that verifies the base expectations. That can also be something I reply incrementally.