Re: [PATCH v3 07/10] PCI: Add 'rcec' field to pci_dev for associated RCiEPs

Bjorn Helgaas
2020-09-02T16:35:08Z

On Wed, Aug 12, 2020 at 09:46:56AM -0700, Sean V Kelley wrote:
> From: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
>
> When attempting error recovery for an RCiEP associated with an RCEC device,
> there needs to be a way to update the Root Error Status, the Uncorrectable
> Error Status and the Uncorrectable Error Severity of the parent RCEC.
> So add the 'rcec' field to the pci_dev structure and provide a hook for the
> Root Port Driver to associate RCiEPs with their respective parent RCEC.

> --- a/drivers/pci/pcie/err.c
> +++ b/drivers/pci/pcie/err.c
> @@ -202,6 +202,12 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
> pci_walk_dev_affected(dev, report_frozen_detected, &status);
> if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_END) {
> status = flr_on_rciep(dev);
> + /*
> + * The callback only clears the Root Error Status
> + * of the RCEC (see aer.c).
> + */
> + if (dev->rcec)
> + reset_link(dev->rcec);
> if (status != PCI_ERS_RESULT_RECOVERED) {
> pci_warn(dev, "function level reset failed\n");
> goto failed;
> @@ -245,7 +251,11 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
> pci_pcie_type(dev) == PCI_EXP_TYPE_RC_EC)) {
> pci_aer_clear_device_status(dev);
> pci_aer_clear_nonfatal_status(dev);
> + } else if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_END && dev->rcec) {
> + pci_aer_clear_device_status(dev->rcec);
> + pci_aer_clear_nonfatal_status(dev->rcec);

Conceptually, I'm not sure why we need the dev->rcec link. The error
was *reported* via the RCEC, so don't we know the RCEC up front,
before we even identify the RCiEP? Can't we just remember that and
dispense with dev->rcec?

I'm also concerned that if we fail to identify the RCiEP (i.e., we
don't have a valid "dev" to use dev->rcec), we will fail to clear the
error status bits. I think it's possible that the RCEC will report an
error, but the RCiEP that generated the error message is not
responding so we can't find it.

> }
> +
> pci_info(dev, "device recovery successful\n");
> return status;
>
> diff --git a/drivers/pci/pcie/portdrv_pci.c b/drivers/pci/pcie/portdrv_pci.c
> index d5b109499b10..a64e88b7166b 100644
> --- a/drivers/pci/pcie/portdrv_pci.c
> +++ b/drivers/pci/pcie/portdrv_pci.c
> @@ -90,6 +90,18 @@ static const struct dev_pm_ops pcie_portdrv_pm_ops = {
> #define PCIE_PORTDRV_PM_OPS NULL
> #endif /* !PM */
>
> +static int pcie_hook_rcec(struct pci_dev *pdev, void *data)
> +{
> + struct pci_dev *rcec = (struct pci_dev *)data;
> +
> + pdev->rcec = rcec;
> + pci_dbg(rcec, "RCiEP(under an RCEC) %04x:%02x:%02x.%d\n",
> + pci_domain_nr(pdev->bus), pdev->bus->number,
> + PCI_SLOT(pdev->devfn), PCI_FUNC(pdev->devfn));

If we do need dev->rcec, this should use pci_name() for the second
device instead of formatting the name manually. I think I would
connect this with the RCiEP instead of the RCEC, e.g.,

pci_dbg(pdev, "PME & error events reported via %s\n", pci_name(rcec));

> +
> + return 0;
> +}
> +
> /*
> * pcie_portdrv_probe - Probe PCI-Express port devices
> * @dev: PCI-Express port device being probed
> @@ -110,6 +122,9 @@ static int pcie_portdrv_probe(struct pci_dev *dev,
> (pci_pcie_type(dev) != PCI_EXP_TYPE_RC_EC)))
> return -ENODEV;
>
> + if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_EC)
> + pcie_walk_rcec(dev, pcie_hook_rcec, dev);
> +
> status = pcie_port_device_register(dev);
> if (status)
> return status;
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index c7fc5726872c..ba29816c827b 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -330,6 +330,7 @@ struct pci_dev {
> #ifdef CONFIG_PCIEPORTBUS
> u16 rcec_cap; /* RCEC capability offset */
> struct rcec_ext *rcec_ext; /* RCEC cached assoc. endpoint extended capabilities */
> + struct pci_dev *rcec; /* Associated RCEC device */
> #endif
> u8 pcie_cap; /* PCIe capability offset */
> u8 msi_cap; /* MSI capability offset */
> --
> 2.28.0
>