linux-kernel - Re: [PATCH v5 26/26] PCI/AER: Unmask RCEC internal errors to enable RCH downstream port error handling

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Message-ID: <20230608192128.GA1210443@bhelgaas>
Date:   Thu, 8 Jun 2023 14:21:28 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Terry Bowman <terry.bowman@....com>
Cc:     alison.schofield@...el.com, vishal.l.verma@...el.com,
        ira.weiny@...el.com, bwidawsk@...nel.org, dan.j.williams@...el.com,
        dave.jiang@...el.com, Jonathan.Cameron@...wei.com,
        linux-cxl@...r.kernel.org, rrichter@....com,
        linux-kernel@...r.kernel.org, bhelgaas@...gle.com
Subject: Re: [PATCH v5 26/26] PCI/AER: Unmask RCEC internal errors to enable
 RCH downstream port error handling

On Wed, Jun 07, 2023 at 05:16:51PM -0500, Terry Bowman wrote:
> From: Robert Richter <rrichter@....com>
> 
> AER corrected and uncorrectable internal errors (CIE/UIE) are masked
> in their corresponding mask registers per default once in power-up
> state. [1][2] Enable internal errors for RCECs to receive CXL
> downstream port errors of Restricted CXL Hosts (RCHs).
> 
> [1] CXL 3.0 Spec, 12.2.1.1 - RCH Downstream Port Detected Errors
> [2] PCIe Base Spec r6.0, 7.8.4.3 Uncorrectable Error Mask Register,
>     7.8.4.6 Correctable Error Mask Register
> 
> Co-developed-by: Terry Bowman <terry.bowman@....com>
> Signed-off-by: Terry Bowman <terry.bowman@....com>
> Signed-off-by: Robert Richter <rrichter@....com>

Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>

> ---
>  drivers/pci/pcie/aer.c | 57 ++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 57 insertions(+)
> 
> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index c354ca5e8f2b..4f9203e27c62 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -948,6 +948,30 @@ static bool find_source_device(struct pci_dev *parent,
>  
>  #ifdef CONFIG_PCIEAER_CXL
>  
> +/**
> + * pci_aer_unmask_internal_errors - unmask internal errors
> + * @dev: pointer to the pcie_dev data structure
> + *
> + * Unmasks internal errors in the Uncorrectable and Correctable Error
> + * Mask registers.
> + *
> + * 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)
> +{
> +	int aer = dev->aer_cap;
> +	u32 mask;
> +
> +	pci_read_config_dword(dev, aer + PCI_ERR_UNCOR_MASK, &mask);
> +	mask &= ~PCI_ERR_UNC_INTN;
> +	pci_write_config_dword(dev, aer + PCI_ERR_UNCOR_MASK, mask);
> +
> +	pci_read_config_dword(dev, aer + PCI_ERR_COR_MASK, &mask);
> +	mask &= ~PCI_ERR_COR_INTERNAL;
> +	pci_write_config_dword(dev, aer + PCI_ERR_COR_MASK, mask);
> +}
> +
>  static bool is_cxl_mem_dev(struct pci_dev *dev)
>  {
>  	/*
> @@ -1027,7 +1051,39 @@ static void cxl_rch_handle_error(struct pci_dev *dev, struct aer_err_info *info)
>  		pcie_walk_rcec(dev, cxl_rch_handle_error_iter, info);
>  }
>  
> +static int handles_cxl_error_iter(struct pci_dev *dev, void *data)
> +{
> +	int *handles_cxl = data;
> +
> +	if (!*handles_cxl)
> +		*handles_cxl = is_cxl_mem_dev(dev) && cxl_error_is_native(dev);
> +
> +	/* Non-zero terminates iteration */
> +	return *handles_cxl;
> +}
> +
> +static bool handles_cxl_errors(struct pci_dev *rcec)
> +{
> +	int handles_cxl = 0;
> +
> +	if (pci_pcie_type(rcec) == PCI_EXP_TYPE_RC_EC &&
> +	    pcie_aer_is_native(rcec))
> +		pcie_walk_rcec(rcec, handles_cxl_error_iter, &handles_cxl);
> +
> +	return !!handles_cxl;
> +}
> +
> +static void cxl_rch_enable_rcec(struct pci_dev *rcec)
> +{
> +	if (!handles_cxl_errors(rcec))
> +		return;
> +
> +	pci_aer_unmask_internal_errors(rcec);
> +	pci_info(rcec, "CXL: Internal errors unmasked");
> +}
> +
>  #else
> +static inline void cxl_rch_enable_rcec(struct pci_dev *dev) { }
>  static inline void cxl_rch_handle_error(struct pci_dev *dev,
>  					struct aer_err_info *info) { }
>  #endif
> @@ -1428,6 +1484,7 @@ static int aer_probe(struct pcie_device *dev)
>  		return status;
>  	}
>  
> +	cxl_rch_enable_rcec(port);
>  	aer_enable_rootport(rpc);
>  	pci_info(port, "enabled with IRQ %d\n", dev->irq);
>  	return 0;
> -- 
> 2.34.1
>