linux-kernel - Re: [PATCH 2/6] cxl/mem: Arrange for always-synchronous memdev attach

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Message-ID: <aTJIIDzBot05PtD_@aschofie-mobl2.lan>
Date: Thu, 4 Dec 2025 18:49:04 -0800
From: Alison Schofield <alison.schofield@...el.com>
To: Dan Williams <dan.j.williams@...el.com>
CC: <dave.jiang@...el.com>, <linux-cxl@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <Smita.KoralahalliChannabasappa@....com>,
	<terry.bowman@....com>, <alejandro.lucero-palau@....com>,
	<linux-pci@...r.kernel.org>, <Jonathan.Cameron@...wei.com>, Alejandro Lucero
	<alucerop@....com>
Subject: Re: [PATCH 2/6] cxl/mem: Arrange for always-synchronous memdev attach

On Wed, Dec 03, 2025 at 06:21:32PM -0800, Dan Williams wrote:
> In preparation for CXL accelerator drivers that have a hard dependency on
> CXL capability initialization, arrange for cxl_mem_probe() to always run
> synchronous with the device_add() of cxl_memdev instances. I.e.
> cxl_mem_driver registration is always complete before the first memdev
> creation event.
> 
> At present, cxl_pci does not care about the attach state of the cxl_memdev
> because all generic memory expansion functionality can be handled by the
> cxl_core. For accelerators, however, that driver needs to perform driver
> specific initialization if CXL is available, or execute a fallback to PCIe
> only operation.
> 
> This synchronous attach guarantee is also needed for Soft Reserve Recovery,
> which is an effort that needs to assert that devices have had a chance to
> attach before making a go / no-go decision on proceeding with CXL subsystem
> initialization.
> 
> By moving devm_cxl_add_memdev() to cxl_mem.ko it removes async module
> loading as one reason that a memdev may not be attached upon return from
> devm_cxl_add_memdev().
> 
> Cc: Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>
> Cc: Alejandro Lucero <alucerop@....com>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>

I did test w this set as a whole, but only giving the Tested-by Tag
to ones exercised in my testing

Tested-by: Alison Schofield <alison.schofield@...el.com>
Reviewed-by: Alison Schofield <alison.schofield@...el.com>