Re: [RESEND v13 17/25] cxl: Introduce cxl_pci_drv_bound() to check for bound driver

Alison Schofield
2025-11-11T08:34:41Z

On Tue, Nov 04, 2025 at 11:02:57AM -0600, 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.

This one was troublesome in cxl-test, more circular dependencies.
I noticed you and GregP chatting about it, so I simply remove it from
the set for now (made all callsites true).

With it gone, the set builds cxl-test and passes the test suite.
I'll watch what happens with this one, and can take another look at
the cxl-test issues if they persist.

A bit below...

snip

> diff --git a/drivers/cxl/pci.c b/drivers/cxl/core/pci_drv.c
> similarity index 99%
> rename from drivers/cxl/pci.c
> rename to drivers/cxl/core/pci_drv.c
> index bd95be1f3d5c..06f2fd993cb0 100644
> --- a/drivers/cxl/pci.c
> +++ b/drivers/cxl/core/pci_drv.c

Needs:
+#include "core.h"

Compiler is warning: no previous prototypes.

snip