linux-kernel - Re: [PATCH 01/15] cxl/aer/pci: Add CXL PCIe port error handler callbacks in AER service driver

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Message-ID: <671705b5bb95b_231229468@dwillia2-xfh.jf.intel.com.notmuch>
Date: Mon, 21 Oct 2024 18:53:57 -0700
From: Dan Williams <dan.j.williams@...el.com>
To: Terry Bowman <terry.bowman@....com>, <ming4.li@...el.com>,
	<linux-cxl@...r.kernel.org>, <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>, <vishal.l.verma@...el.com>,
	<dan.j.williams@...el.com>, <bhelgaas@...gle.com>, <mahesh@...ux.ibm.com>,
	<oohall@...il.com>, <Benjamin.Cheatham@....com>, <rrichter@....com>,
	<nathan.fontenot@....com>, <smita.koralahallichannabasappa@....com>
Subject: Re: [PATCH 01/15] cxl/aer/pci: Add CXL PCIe port error handler
 callbacks in AER service driver

Terry Bowman wrote:
> CXL protocol errors are reported to the OS through PCIe correctable and
> uncorrectable internal errors. However, since CXL PCIe port devices
> are currently bound to the portdrv driver, there is no mechanism to
> notify the CXL driver, which is necessary for proper logging and
> handling.
> 
> To address this, introduce CXL PCIe port error callbacks along with
> register/unregister and accessor functions. The callbacks will be
> invoked by the AER driver in the case protocol errors are reported by
> a CXL port device.
> 
> The AER driver callbacks will be used in future patches implementing
> CXL PCIe port error handling.
> 
> Signed-off-by: Terry Bowman <terry.bowman@....com>
> ---
>  drivers/pci/pcie/aer.c | 22 ++++++++++++++++++++++
>  include/linux/aer.h    | 14 ++++++++++++++
>  2 files changed, 36 insertions(+)
> 
> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index 13b8586924ea..a9792b9576b4 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -50,6 +50,8 @@ struct aer_rpc {
>  	DECLARE_KFIFO(aer_fifo, struct aer_err_source, AER_ERROR_SOURCES_MAX);
>  };
>  
> +static struct cxl_port_err_hndlrs cxl_port_hndlrs;

I think this can afford to splurge on a few more letters and make this

static struct cxl_port_error_handlers cxl_port_error_handlers;


> +
>  /* AER stats for the device */
>  struct aer_stats {
>  
> @@ -1078,6 +1080,26 @@ static inline void cxl_rch_handle_error(struct pci_dev *dev,
>  					struct aer_err_info *info) { }
>  #endif
>  
> +void register_cxl_port_hndlrs(struct cxl_port_err_hndlrs *_cxl_port_hndlrs)
> +{
> +	cxl_port_hndlrs.error_detected = _cxl_port_hndlrs->error_detected;
> +	cxl_port_hndlrs.cor_error_detected = _cxl_port_hndlrs->cor_error_detected;
> +}
> +EXPORT_SYMBOL_NS_GPL(register_cxl_port_hndlrs, CXL);
> +
> +void unregister_cxl_port_hndlrs(void)
> +{
> +	cxl_port_hndlrs.error_detected = NULL;
> +	cxl_port_hndlrs.cor_error_detected = NULL;
> +}
> +EXPORT_SYMBOL_NS_GPL(unregister_cxl_port_hndlrs, CXL);
> +
> +struct cxl_port_err_hndlrs *find_cxl_port_hndlrs(void)
> +{
> +	return &cxl_port_hndlrs;
> +}
> +EXPORT_SYMBOL_NS_GPL(find_cxl_port_hndlrs, CXL);

I guess I will need to go deeper into the code, but I would not have
expected that new registration interfaces are needed. Each 'struct
pci_driver' could optionally include CXL error handlers alongside their
PCIe error handlers and when CXL AER errors are broadcast only the CXL
handlers are invoked. I.e. the registration is something like:

diff --git a/drivers/pci/pcie/portdrv.c b/drivers/pci/pcie/portdrv.c
index 6af5e0425872..42db26195bda 100644
--- a/drivers/pci/pcie/portdrv.c
+++ b/drivers/pci/pcie/portdrv.c
@@ -793,6 +793,7 @@ static struct pci_driver pcie_portdriver = {
        .shutdown       = pcie_portdrv_shutdown,
 
        .err_handler    = &pcie_portdrv_err_handler,
+       .cxl_err_handler = &cxl_portdrv_err_handler,
 
        .driver_managed_dma = true,