Re: [PATCH v10 05/17] CXL/AER: Introduce kfifo for forwarding CXL errors

[Jonathan Cameron <Jonathan.Cameron@huawei.com>]

On Thu, 26 Jun 2025 17:42:40 -0500
Terry Bowman <terry.bowman@amd.com> wrote:

> CXL error handling will soon be moved from the AER driver into the CXL
> driver. This requires a notification mechanism for the AER driver to share
> the AER interrupt with the CXL driver. The notification will be used
> as an indication for the CXL drivers to handle and log the CXL RAS errors.
> 
> First, introduce cxl/core/native_ras.c to contain changes for the CXL
> driver's RAS native handling. This as an alternative to dropping the
> changes into existing cxl/core/ras.c file with purpose to avoid #ifdefs.
> Introduce CXL Kconfig CXL_NATIVE_RAS, dependent on PCIEAER_CXL, to
> conditionally compile the new file.
> 
> Add a kfifo work queue to be used by the AER driver and CXL driver. The AER
> driver will be the sole kfifo producer adding work and the cxl_core will be
> the sole kfifo consumer removing work. Add the boilerplate kfifo support.
> 
> Add CXL work queue handler registration functions in the AER driver. Export
> the functions allowing CXL driver to access. Implement registration
> functions for the CXL driver to assign or clear the work handler function.
> 
> Introduce 'struct cxl_proto_err_info' to serve as the kfifo work data. This
> will contain the erring device's PCI SBDF details used to rediscover the
> device after the CXL driver dequeues the kfifo work. The device rediscovery
> will be introduced along with the CXL handling in future patches.
> 
> Signed-off-by: Terry Bowman <terry.bowman@amd.com>
Hi Terry,

Whilst it obviously makes patch preparation a bit more time consuming
for series like this with many patches it can be useful to add a brief
change log to the individual patches as well as the cover letter.
That helps reviewers figure out where they need to look again.

A few trivial things inline.

With those fixed up
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

Jonathan


> ---
>  drivers/cxl/Kconfig           | 14 ++++++++
>  drivers/cxl/core/Makefile     |  1 +
>  drivers/cxl/core/core.h       |  8 +++++
>  drivers/cxl/core/native_ras.c | 26 +++++++++++++++
>  drivers/cxl/core/port.c       |  2 ++
>  drivers/cxl/core/ras.c        |  1 +
>  drivers/cxl/cxlpci.h          |  1 +
>  drivers/pci/pci.h             |  4 +++
>  drivers/pci/pcie/aer.c        |  7 ++--
>  drivers/pci/pcie/cxl_aer.c    | 60 +++++++++++++++++++++++++++++++++++
>  include/linux/aer.h           | 31 ++++++++++++++++++
>  11 files changed, 153 insertions(+), 2 deletions(-)
>  create mode 100644 drivers/cxl/core/native_ras.c


>  static void cxl_cper_trace_corr_port_prot_err(struct pci_dev *pdev,
> diff --git a/drivers/cxl/cxlpci.h b/drivers/cxl/cxlpci.h
> index 54e219b0049e..6f1396ef7b77 100644
> --- a/drivers/cxl/cxlpci.h
> +++ b/drivers/cxl/cxlpci.h
> @@ -4,6 +4,7 @@
>  #define __CXL_PCI_H__
>  #include <linux/pci.h>
>  #include "cxl.h"
> +#include "linux/aer.h"

Why?  There are no changes in this header other than the include and the changes
to linux/aer.h are new stuff so I can't see how it becomes necessary if it
wasn't before.

Might well have always been missing and should have been here. If so separate
patch to tidy that up.

>  
>  #define CXL_MEMORY_PROGIF	0x10
>  


> diff --git a/drivers/pci/pcie/cxl_aer.c b/drivers/pci/pcie/cxl_aer.c
> index b2ea14f70055..846ab55d747c 100644
> --- a/drivers/pci/pcie/cxl_aer.c
> +++ b/drivers/pci/pcie/cxl_aer.c

>  static int cxl_rch_handle_error_iter(struct pci_dev *dev, void *data)
>  {
>  	struct aer_err_info *info = (struct aer_err_info *)data;
> @@ -136,3 +152,47 @@ void cxl_rch_enable_rcec(struct pci_dev *rcec)
>  	pci_info(rcec, "CXL: Internal errors unmasked");
>  }
>  
> +static DEFINE_KFIFO(cxl_proto_err_fifo, struct cxl_proto_err_work_data,
> +		    CXL_ERROR_SOURCES_MAX);
> +static DEFINE_SPINLOCK(cxl_proto_err_fifo_lock);
> +struct work_struct *cxl_proto_err_work;

I'm not seeing a declaration for this in the headers, so can it be static?

This is made a little more confusing as in this patch we have both
a structure called cxl_proto_err_work and a pointer to it with exactly the
same name.  Maybe rename this so it's subtly different.  cxl_protocol_err_work
or something silly like that just to make reviewers life a tiny bit easier!

> +

> diff --git a/include/linux/aer.h b/include/linux/aer.h
> index 02940be66324..24c3d9e18ad5 100644
> --- a/include/linux/aer.h
> +++ b/include/linux/aer.h
> @@ -10,6 +10,7 @@
>  
>  #include <linux/errno.h>
>  #include <linux/types.h>
> +#include <linux/workqueue_types.h>
>  
>  #define AER_NONFATAL			0
>  #define AER_FATAL			1
> @@ -53,6 +54,26 @@ struct aer_capability_regs {
>  	u16 uncor_err_source;
>  };
>  
> +/**
> + * struct cxl_proto_err_info - Error information used in CXL error handling
> + * @severity: AER severity
> + * @function: Device's PCI function

Run kernel-doc over the files and fix errors / warning.
Missed updating this to devfn which it would have shouted about.

> + * @device: Device's PCI device
> + * @bus: Device's PCI bus
> + * @segment: Device's PCI segment
> + */
> +struct cxl_proto_error_info {
> +	int severity;
> +
> +	u8 devfn;
> +	u8 bus;
> +	u16 segment;
> +};