linux-kernel - Re: [PATCH v11 16/23] cxl/pci: Introduce CXL Endpoint protocol error handlers

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Message-ID: <20250910142335.00001f53@huawei.com>
Date: Wed, 10 Sep 2025 14:23:35 +0100
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: Terry Bowman <terry.bowman@....com>
CC: <dave@...olabs.net>, <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>,
	<Benjamin.Cheatham@....com>, <sathyanarayanan.kuppuswamy@...ux.intel.com>,
	<linux-cxl@...r.kernel.org>, <alucerop@....com>, <ira.weiny@...el.com>,
	<linux-kernel@...r.kernel.org>, <linux-pci@...r.kernel.org>
Subject: Re: [PATCH v11 16/23] cxl/pci: Introduce CXL Endpoint protocol
 error handlers

On Tue, 26 Aug 2025 20:35:31 -0500
Terry Bowman <terry.bowman@....com> wrote:

> CXL Endpoint protocol errors are currently handled using PCI error
> handlers. The CXL Endpoint requires CXL specific handling in the case of
> uncorrectable error (UCE) handling not provided by the PCI handlers.
> 
> Add CXL specific handlers for CXL Endpoints. Rename the existing
> cxl_error_handlers to be pci_error_handlers to more correctly indicate
> the error type and follow naming consistency.
> 
> The PCI handlers will be called if the CXL device is not trained for
> alternate protocol (CXL). Update the CXL Endpoint PCI handlers to call the
> CXL UCE handlers.
> 
> The existing EP UCE handler includes checks for various results. These are
> no longer needed because CXL UCE recovery will not be attempted. Implement
> cxl_handle_ras() to return PCI_ERS_RESULT_NONE or PCI_ERS_RESULT_PANIC. The
> CXL UCE handler is called by cxl_do_recovery() that acts on the return
> value. In the case of the PCI handler path, call panic() if the result is
> PCI_ERS_RESULT_PANIC.
> 
> Signed-off-by: Terry Bowman <terry.bowman@....com>
> Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> 
> ---
> Changes in v10->v11:
> - cxl_error_detected() - Change handlers' scoped_guard() to guard() (Jonathan)
> - cxl_error_detected() - Remove extra line (Shiju)
> - Changes moved to core/ras.c (Terry)
> - cxl_error_detected(), remove 'ue' and return with function call. (Jonathan)
> - Remove extra space in documentation for PCI_ERS_RESULT_PANIC definition
> - Move #include "pci.h from cxl.h to core.h (Terry)
> - Remove unnecessary includes of cxl.h and core.h in mem.c (Terry)
Hi Terry,

A few suggested renames inline just because things like pci_cor_error_detected()
sounds like it should have nothing CXL specific in it. 

Whilst it is clunky to use cxl_pci_cor_error_detected() I think that is
worth doing to avoid this potential confusion.

> diff --git a/drivers/cxl/core/ras.c b/drivers/cxl/core/ras.c
> index 42b6e0b092d5..b285448c2d9c 100644
> --- a/drivers/cxl/core/ras.c
> +++ b/drivers/cxl/core/ras.c

>  
> -void cxl_cor_error_detected(struct pci_dev *pdev)
> +void cxl_cor_error_detected(struct device *dev)
>  {
> +	struct pci_dev *pdev = to_pci_dev(dev);
>  	struct cxl_dev_state *cxlds = pci_get_drvdata(pdev);
> -	struct device *dev = &cxlds->cxlmd->dev;
> +	struct device *cxlmd_dev = &cxlds->cxlmd->dev;
>  
> -	scoped_guard(device, dev) {

Dropping the scoped_guard() to guard() here makes it harder
to tell what is going on.  I guess it isn't quite worth a precursor
patch unless there are several similar refactors to do.

> -		if (!dev->driver) {
> -			dev_warn(&pdev->dev,
> -				 "%s: memdev disabled, abort error handling\n",
> -				 dev_name(dev));
> -			return;
> -		}
> +	guard(device)(cxlmd_dev);
>  
> -		if (cxlds->rcd)
> -			cxl_handle_rdport_errors(cxlds);
> -
> -		cxl_handle_cor_ras(&cxlds->cxlmd->dev, cxlds->serial, cxlds->regs.ras);
> +	if (!cxlmd_dev->driver) {
> +		dev_warn(&pdev->dev, "%s: memdev disabled, abort error handling", dev_name(dev));
> +		return;
>  	}
> +
> +	if (cxlds->rcd)
> +		cxl_handle_rdport_errors(cxlds);
> +
> +	cxl_handle_cor_ras(&cxlds->cxlmd->dev, cxlds->serial, cxlds->regs.ras);
>  }
>  EXPORT_SYMBOL_NS_GPL(cxl_cor_error_detected, "CXL");
>  
> -pci_ers_result_t cxl_error_detected(struct pci_dev *pdev,
> -				    pci_channel_state_t state)
> +void pci_cor_error_detected(struct pci_dev *pdev)
>  {
> +	cxl_cor_error_detected(&pdev->dev);
> +}
> +EXPORT_SYMBOL_NS_GPL(pci_cor_error_detected, "CXL");

I'd go with a cxl_pci_ prefix for this to avoid impression it is is more
generic than that.

>
> +
> +pci_ers_result_t pci_error_detected(struct pci_dev *pdev,

Given this is CXL specific, probably makes sense to prefix to give
cxl_pci_error_detected()


Then when we see the call it is more obvious it isn't a 'generic'
PCI thing.


> +				    pci_channel_state_t error)
> +{
> +	pci_ers_result_t rc;
> +
> +	rc = cxl_error_detected(&pdev->dev);
> +	if (rc == PCI_ERS_RESULT_PANIC)
> +		panic("CXL cachemem error.");
> +
> +	return rc;
> +}
> +EXPORT_SYMBOL_NS_GPL(pci_error_detected, "CXL");