Re: [PATCH v7 05/17] PCI/AER: Add CXL PCIe Port correctable error support in AER service driver

Bjorn Helgaas
2025-02-11T20:28:53Z

On Tue, Feb 11, 2025 at 01:24:32PM -0600, Terry Bowman wrote:
> The AER service driver supports handling Downstream Port Protocol Errors in
> Restricted CXL host (RCH) mode also known as CXL1.1. It needs the same
> functionality for CXL PCIe Ports operating in Virtual Hierarchy (VH)
> mode.[1]
>
> CXL and PCIe Protocol Error handling have different requirements that
> necessitate a separate handling path. The AER service driver may try to
> recover PCIe uncorrectable non-fatal errors (UCE). The same recovery is not
> suitable for CXL PCIe Port devices because of potential for system memory
> corruption. Instead, CXL Protocol Error handling must use a kernel panic
> in the case of a fatal or non-fatal UCE. The AER driver's PCIe Protocol
> Error handling does not panic the kernel in response to a UCE.
>
> Introduce a separate path for CXL Protocol Error handling in the AER
> service driver. This will allow CXL Protocol Errors to use CXL specific
> handling instead of PCIe handling. Add the CXL specific changes without
> affecting or adding functionality in the PCIe handling.
>
> Make this update alongside the existing Downstream Port RCH error handling
> logic, extending support to CXL PCIe Ports in VH mode.
>
> Remove is_internal_error(). is_internal_error() was used to determine if
> an AER error was a CXL error. Instead, now rely on pcie_is_cxl_port() to
> indicate the error is a CXL error.
>
> The uncorrectable error (UCE) handling will be added in a future patch.
>
> [1] CXL 3.1 Spec, 12.2.2 CXL Root Ports, Downstream Switch Ports, and
> Upstream Switch Ports
>
> Signed-off-by: Terry Bowman <terry.bowman@amd.com>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> Reviewed-by: Ira Weiny <ira.weiny@intel.com>

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

> ---
> drivers/pci/pcie/aer.c | 47 ++++++++++++++++++++++++++++--------------
> 1 file changed, 32 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
> index f99a1c6fb274..34ec0958afff 100644
> --- a/drivers/pci/pcie/aer.c
> +++ b/drivers/pci/pcie/aer.c
> @@ -989,14 +989,6 @@ static bool cxl_error_is_native(struct pci_dev *dev)
> return (pcie_ports_native || host->native_aer);
> }
>
> -static bool is_internal_error(struct aer_err_info *info)
> -{
> - if (info->severity == AER_CORRECTABLE)
> - return info->status & PCI_ERR_COR_INTERNAL;
> -
> - return info->status & PCI_ERR_UNC_INTN;
> -}
> -
> static int cxl_rch_handle_error_iter(struct pci_dev *dev, void *data)
> {
> struct aer_err_info *info = (struct aer_err_info *)data;
> @@ -1033,9 +1025,23 @@ static void cxl_handle_error(struct pci_dev *dev, struct aer_err_info *info)
> * RCH's downstream port. Check and handle them in the CXL.mem
> * device driver.
> */
> - if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_EC &&
> - is_internal_error(info))
> - pcie_walk_rcec(dev, cxl_rch_handle_error_iter, info);
> + if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_EC)
> + return pcie_walk_rcec(dev, cxl_rch_handle_error_iter, info);
> +
> + if (info->severity == AER_CORRECTABLE) {
> + struct pci_driver *pdrv = dev->driver;
> + int aer = dev->aer_cap;
> +
> + if (aer)
> + pci_write_config_dword(dev, aer + PCI_ERR_COR_STATUS,
> + info->status);
> +
> + if (pdrv && pdrv->cxl_err_handler &&
> + pdrv->cxl_err_handler->cor_error_detected)
> + pdrv->cxl_err_handler->cor_error_detected(dev);
> +
> + pcie_clear_device_status(dev);
> + }
> }
>
> static int handles_cxl_error_iter(struct pci_dev *dev, void *data)
> @@ -1053,9 +1059,13 @@ static bool handles_cxl_errors(struct pci_dev *dev)
> {
> bool handles_cxl = false;
>
> - if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_EC &&
> - pcie_aer_is_native(dev))
> + if (!pcie_aer_is_native(dev))
> + return false;
> +
> + if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_EC)
> pcie_walk_rcec(dev, handles_cxl_error_iter, &handles_cxl);
> + else
> + handles_cxl = pcie_is_cxl_port(dev);
>
> return handles_cxl;
> }
> @@ -1073,6 +1083,10 @@ static void cxl_enable_internal_errors(struct pci_dev *dev)
> static inline void cxl_enable_internal_errors(struct pci_dev *dev) { }
> static inline void cxl_handle_error(struct pci_dev *dev,
> struct aer_err_info *info) { }
> +static bool handles_cxl_errors(struct pci_dev *dev)
> +{
> + return false;
> +}
> #endif
>
> /**
> @@ -1110,8 +1124,11 @@ static void pci_aer_handle_error(struct pci_dev *dev, struct aer_err_info *info)
>
> static void handle_error_source(struct pci_dev *dev, struct aer_err_info *info)
> {
> - cxl_handle_error(dev, info);
> - pci_aer_handle_error(dev, info);
> + if (handles_cxl_errors(dev))
> + cxl_handle_error(dev, info);
> + else
> + pci_aer_handle_error(dev, info);
> +
> pci_dev_put(dev);
> }
>
> --
> 2.34.1
>