Re: [PATCH v4 23/23] PCI/AER: Unmask RCEC internal errors to enable RCH downstream port error handling

Bjorn Helgaas
2023-05-24T21:45:14Z

On Tue, May 23, 2023 at 06:22:14PM -0500, Terry Bowman wrote:
> From: Robert Richter <rrichter@amd.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 6.0, 7.8.4.3 Uncorrectable Error Mask Register,
> 7.8.4.6 Correctable Error Mask Register

I use "r6.0" to make sure it isn't mistaken for a section number.

> Co-developed-by: Terry Bowman <terry.bowman@amd.com>
> Signed-off-by: Terry Bowman <terry.bowman@amd.com>
> Signed-off-by: Robert Richter <rrichter@amd.com>
> ---
> drivers/pci/pcie/aer.c | 64 ++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 64 insertions(+)
>
> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index 2e3f00b6a5bd..c5076ae4eb58 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -948,6 +948,32 @@ static bool find_source_device(struct pci_dev *parent,
>
> #ifdef CONFIG_PCIEAER_CXL
>
> +static int pci_aer_unmask_internal_errors(struct pci_dev *dev)
> +{
> + int aer, rc;
> + u32 mask;
> +
> + if (!pcie_aer_is_native(dev))
> + return -EIO;
> +
> + aer = dev->aer_cap;
> + rc = pci_read_config_dword(dev, aer + PCI_ERR_UNCOR_MASK, &mask);
> + if (rc)
> + return rc;

I don't think there's much value in checking all these config accesses
for failure. A failure return really just means you called it with
invalid parameters; it doesn't tell you whether it was successful on
PCI.

> + mask &= ~PCI_ERR_UNC_INTN;
> + rc = pci_write_config_dword(dev, aer + PCI_ERR_UNCOR_MASK, mask);
> + if (rc)
> + return rc;
> +
> + rc = pci_read_config_dword(dev, aer + PCI_ERR_COR_MASK, &mask);
> + if (rc)
> + return rc;
> + mask &= ~PCI_ERR_COR_INTERNAL;
> + rc = pci_write_config_dword(dev, aer + PCI_ERR_COR_MASK, mask);
> +
> + return rc;
> +}
> +
> static bool is_cxl_mem_dev(struct pci_dev *dev)
> {
> /*
> @@ -1031,7 +1057,44 @@ 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;
> +
> + *handles_cxl = is_cxl_mem_dev(dev) && cxl_error_is_native(dev);

This effectively only looks at the *last* RCiEP associated with this
RCEC. I would expect a logical OR of all of them.

I see this is another use of is_cxl_mem_dev() and
cxl_error_is_native() that really requires them to be in this file.

> + 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;
> +
> + /*
> + * Internal errors are masked by default, unmask RCEC's here
> + * PCI6.0 7.8.4.3 Uncorrectable Error Mask Register (Offset 08h)
> + * PCI6.0 7.8.4.6 Correctable Error Mask Register (Offset 14h)

The spec references seem superfluous here. The PCI_ERR_UNCOR_MASK and
PCI_ERR_COR_MASK in pci_aer_unmask_internal_errors() are pretty good
pointers.

> + */
> + if (pci_aer_unmask_internal_errors(rcec))
> + pci_err(rcec, "CXL: Failed to unmask internal errors");
> + else
> + 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
> @@ -1432,6 +1495,7 @@ static int aer_probe(struct pcie_device *dev)
> return status;
> }
>
> + cxl_rch_enable_rcec(port);

Could this be done by the driver that claims the CXL RCiEP? There's
no point in unmasking the errors before there's a driver with
pci_error_handlers that can do something with them anyway.

> aer_enable_rootport(rpc);
> pci_info(port, "enabled with IRQ %d\n", dev->irq);
> return 0;
> --
> 2.34.1
>