Re: [RFC PATCH 6/9] PCI: Add 'rcec' field to pci_dev for associated RCiEPs

Sean V Kelley
2020-07-27T15:39:47Z

On 27 Jul 2020, at 4:23, Jonathan Cameron wrote:

> On Fri, 24 Jul 2020 10:22:20 -0700
> Sean V Kelley <sean.v.kelley@intel.com> 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.
>>
>> Co-developed-by: Sean V Kelley <sean.v.kelley@intel.com>
>> Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
>> Signed-off-by: Sean V Kelley <sean.v.kelley@intel.com>
>
> I haven't tested yet, but I think there is one path in here that
> breaks
> my case (no OS visible rcec / all done in firmware GHESv2 / APEI)
>
> Jonathan

Okay, keep me up to date and if there is a way I can reproduce or better
test for your use case let me know and I will do so.

>
>> ---
>> drivers/pci/pcie/aer.c | 9 +++++----
>> drivers/pci/pcie/err.c | 9 +++++++++
>> drivers/pci/pcie/portdrv_pci.c | 15 +++++++++++++++
>> include/linux/pci.h | 3 +++
>> 4 files changed, 32 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c
>> index 3acf56683915..f1bf06be449e 100644
>> --- a/drivers/pci/pcie/aer.c
>> +++ b/drivers/pci/pcie/aer.c
>> @@ -1335,17 +1335,18 @@ static int aer_probe(struct pcie_device *dev)
>> static pci_ers_result_t aer_root_reset(struct pci_dev *dev)
>> {
>> int aer = dev->aer_cap;
>> + int rc = 0;
>> u32 reg32;
>> - int rc;
>> -
>>
>> /* Disable Root's interrupt in response to error messages */
>> pci_read_config_dword(dev, aer + PCI_ERR_ROOT_COMMAND, &reg32);
>> reg32 &= ~ROOT_PORT_INTR_ON_MESG_MASK;
>> pci_write_config_dword(dev, aer + PCI_ERR_ROOT_COMMAND, reg32);
>>
>> - rc = pci_bus_error_reset(dev);
>> - pci_info(dev, "Root Port link has been reset\n");
>> + if (pci_pcie_type(dev) != PCI_EXP_TYPE_RC_EC) {
>> + rc = pci_bus_error_reset(dev);
>> + pci_info(dev, "Root Port link has been reset\n");
>> + }
>>
>> /* Clear Root Error Status */
>> pci_read_config_dword(dev, aer + PCI_ERR_ROOT_STATUS, &reg32);
>> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
>> index 9b3ec94bdf1d..0aae7643132e 100644
>> --- a/drivers/pci/pcie/err.c
>> +++ b/drivers/pci/pcie/err.c
>> @@ -203,6 +203,11 @@ 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).
>> + */
>> + reset_link(dev->rcec);
>
> This looks dangerous for my case where APEI / GHESv2 is used. In that
> case
> we don't expose an RCEC at all. I don't think the reset_link
> callback
> is safe to a null pointer here. Fix may be as simple as
> if (dev->rcec)
> reset_link(dev->rcec);

Good catch. Will look to NULL case as well as walk through code where
dev->rcec is further referenced (below and elsewhere) to ensure nothing
falls through. Glad you are pointing these out.

>
>
>> if (status != PCI_ERS_RESULT_RECOVERED) {
>> pci_warn(dev, "function level reset failed\n");
>> goto failed;
>> @@ -246,7 +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) {
>> + pci_aer_clear_device_status(dev->rcec);
>> + pci_aer_clear_nonfatal_status(dev->rcec);
>
> These may be safe as in my both now have protections for
> !pcie_aer_is_native.
>
I’ll have a look again for the NULL case

>> }
>> +
>> 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..f9409a0110c2 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_info(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));
>
> We may want to make this debug info at somepoint if we have a way
> of discovering it from userspace. The PCI boot up is extremely
> verbose already!

I’ve submitted patches to pciutils, which expose this very detail:

https://lore.kernel.org/linux-pci/20200624223940.240463-1-sean.v.kelley@linux.intel.com/

Flexible either way, could remove or make it debug info.

Thanks,

Sean

>
>> +
>> + 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 34c1c4f45288..e920f29df40b 100644
>> --- a/include/linux/pci.h
>> +++ b/include/linux/pci.h
>> @@ -326,6 +326,9 @@ struct pci_dev {
>> #ifdef CONFIG_PCIEAER
>> u16 aer_cap; /* AER capability offset */
>> struct aer_stats *aer_stats; /* AER stats for this device */
>> +#endif
>> +#ifdef CONFIG_PCIEPORTBUS
>> + struct pci_dev *rcec; /* Associated RCEC device */
>> #endif
>> u8 pcie_cap; /* PCIe capability offset */
>> u8 msi_cap; /* MSI capability offset */