linux-kernel - Re: [PATCH v12 19/25] cxl: Introduce cxl_pci_drv

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Message-ID: <0d139f83-36a0-4f67-8a2e-421ad1c8663e@amd.com>
Date: Fri, 3 Oct 2025 15:12:41 -0500
From: "Cheatham, Benjamin" <benjamin.cheatham@....com>
To: Terry Bowman <terry.bowman@....com>
CC: <linux-kernel@...r.kernel.org>, <linux-pci@...r.kernel.org>,
	<dave@...olabs.net>, <jonathan.cameron@...wei.com>, <dave.jiang@...el.com>,
	<alison.schofield@...el.com>, <dan.j.williams@...el.com>,
	<bhelgaas@...gle.com>, <shiju.jose@...wei.com>, <ming.li@...omail.com>,
	<Smita.KoralahalliChannabasappa@....com>, <rrichter@....com>,
	<dan.carpenter@...aro.org>, <PradeepVineshReddy.Kodamati@....com>,
	<lukas@...ner.de>, <sathyanarayanan.kuppuswamy@...ux.intel.com>,
	<linux-cxl@...r.kernel.org>, <alucerop@....com>, <ira.weiny@...el.com>,
	<linux-cxl@...r.kernel.org>
Subject: Re: [PATCH v12 19/25] cxl: Introduce cxl_pci_drv_bound() to check for
 bound driver

On 9/25/2025 5:34 PM, Terry Bowman wrote:
> CXL devices handle protocol errors via driver-specific callbacks rather
> than the generic pci_driver::err_handlers by default. The callbacks are
> implemented in the cxl_pci driver and are not part of struct pci_driver, so
> cxl_core must verify that a device is actually bound to the cxl_pci
> module's driver before invoking the callbacks (the device could be bound
> to another driver, e.g. VFIO).
> 
> However, cxl_core can not reference symbols in the cxl_pci module because
> it creates a circular dependency. This prevents cxl_core from checking the
> EP's bound driver and calling the callbacks.
> 
> To fix this, move drivers/cxl/pci.c into drivers/cxl/core/pci_drv.c and
> build it as part of the cxl_core module. Compile into cxl_core using
> CXL_PCI and CXL_CORE Kconfig dependencies. This removes the standalone cxl_pci
> module, consolidates the cxl_pci driver code into cxl_core, and eliminates
> the circular dependency so cxl_core can safely perform bound-driver checks
> and invoke the CXL PCI callbacks.
> 
> Introduce cxl_pci_drv_bound() to return boolean depending on if the PCI EP
> parameter is bound to a CXL driver instance. This will be used in future
> patch when dequeuing work from the kfifo.
> 
> Signed-off-by: Terry Bowman <terry.bowman@....com>
> 
> ---

Reviewed-by: Ben Cheatham <benjamin.cheatham@....com>