linux-kernel - Re: [RFC PATCH 8/9] PCI/AER: Export pci_aer_unmask_internal

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Message-ID: <20240710214744.GA261828@bhelgaas>
Date: Wed, 10 Jul 2024 16:47:44 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Terry Bowman <terry.bowman@....com>
Cc: dan.j.williams@...el.com, ira.weiny@...el.com, dave@...olabs.net,
	dave.jiang@...el.com, alison.schofield@...el.com,
	ming4.li@...el.com, vishal.l.verma@...el.com,
	jim.harris@...sung.com, ilpo.jarvinen@...ux.intel.com,
	ardb@...nel.org, sathyanarayanan.kuppuswamy@...ux.intel.com,
	linux-cxl@...r.kernel.org, linux-kernel@...r.kernel.org,
	Yazen.Ghannam@....com, Robert.Richter@....com,
	Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org
Subject: Re: [RFC PATCH 8/9] PCI/AER: Export pci_aer_unmask_internal_errors()

On Mon, Jun 17, 2024 at 03:04:10PM -0500, Terry Bowman wrote:
> AER correctable internal errors (CIE) and AER uncorrectable internal
> errors (UIE) are disabled through the AER mask register by default.[1]

Nit: "Correctable Errors" and "Uncorrectable Errors" are generic PCIe
concepts that exist independent of AER, so I wouldn't prefix them with
AER.  The AER mask registers control *reporting* of errors, but of
course they don't disable the errors themselves.

> CXL PCIe ports use the CIE/UIE to report RAS errors and as a result
> need CIE/UIE enabled.[2]
> 
> Change pci_aer_unmask_internal_errors() function to be exported for
> the CXL driver and other drivers to use.
> 
> [1] PCI6.0 - 7.8.4.3 Uncorrectable

s/PCI6.0 .../PCIe r6.0, sec 7.8.4.3/ since there is a conventional PCI
spec as well.

> [2] CXL3.1 - 12.2.2 CXL Root Ports, Downstream Switch Ports, and Upstream
>              Switch Ports
> 
> Signed-off-by: Terry Bowman <terry.bowman@....com>
> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> Cc: linux-pci@...r.kernel.org
> ---
>  drivers/pci/pcie/aer.c | 3 ++-
>  include/linux/aer.h    | 6 ++++++
>  2 files changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index 4dc03cb9aff0..d7a1982f0c50 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -951,7 +951,7 @@ static bool find_source_device(struct pci_dev *parent,
>   * Note: AER must be enabled and supported by the device which must be
>   * checked in advance, e.g. with pcie_aer_is_native().
>   */
> -static void pci_aer_unmask_internal_errors(struct pci_dev *dev)
> +void pci_aer_unmask_internal_errors(struct pci_dev *dev)
>  {
>  	int aer = dev->aer_cap;
>  	u32 mask;
> @@ -964,6 +964,7 @@ static void pci_aer_unmask_internal_errors(struct pci_dev *dev)
>  	mask &= ~PCI_ERR_COR_INTERNAL;
>  	pci_write_config_dword(dev, aer + PCI_ERR_COR_MASK, mask);
>  }
> +EXPORT_SYMBOL_GPL(pci_aer_unmask_internal_errors);
>  
>  static bool is_cxl_mem_dev(struct pci_dev *dev)
>  {
> diff --git a/include/linux/aer.h b/include/linux/aer.h
> index 4b97f38f3fcf..a4fd25ea0280 100644
> --- a/include/linux/aer.h
> +++ b/include/linux/aer.h
> @@ -50,6 +50,12 @@ static inline int pci_aer_clear_nonfatal_status(struct pci_dev *dev)
>  static inline int pcie_aer_is_native(struct pci_dev *dev) { return 0; }
>  #endif
>  
> +#ifdef CONFIG_PCIEAER_CXL
> +void pci_aer_unmask_internal_errors(struct pci_dev *dev);
> +#else
> +static inline void pci_aer_unmask_internal_errors(struct pci_dev *dev) { }
> +#endif

I don't like the idea of exporting a generic PCI interface that only
does something when CONFIG_PCIEAER_CXL is enabled.  If there's ever a
non-CXL caller, it will be confused.

Bjorn