Re: [RFC PATCH 1/9] PCI/AER: Update AER driver to call root port and downstream port UCE handlers

fan
2024-07-11T01:14:41Z

On Wed, Jul 10, 2024 at 04:48:09PM -0500, Terry Bowman wrote:
> Hi Fan,
>
> On 7/10/24 15:48, nifan.cxl@gmail.com wrote:
> > On Mon, Jun 24, 2024 at 12:56:29PM -0500, Terry Bowman wrote:
> >> Hi Dan,
> >>
> >> I added a response below.
> >>
> >> On 6/21/24 14:17, Dan Williams wrote:
> >>> Terry Bowman wrote:
> >>>> The AER service driver does not currently call a handler for AER
> >>>> uncorrectable errors (UCE) detected in root ports or downstream
> >>>> ports. This is not needed in most cases because common PCIe port
> >>>> functionality is handled by portdrv service drivers.
> >>>>
> >>>> CXL root ports include CXL specific RAS registers that need logging
> >>>> before starting do_recovery() in the UCE case.
> >>>>
> >>>> Update the AER service driver to call the UCE handler for root ports
> >>>> and downstream ports. These PCIe port devices are bound to the portdrv
> >>>> driver that includes a CE and UCE handler to be called.
> >>>>
> >>>> Signed-off-by: Terry Bowman <terry.bowman@amd.com>
> >>>> Cc: Bjorn Helgaas <bhelgaas@google.com>
> >>>> Cc: linux-pci@vger.kernel.org
> >>>> ---
> >>>> drivers/pci/pcie/err.c | 20 ++++++++++++++++++++
> >>>> 1 file changed, 20 insertions(+)
> >>>>
> >>>> diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
> >>>> index 705893b5f7b0..a4db474b2be5 100644
> >>>> --- a/drivers/pci/pcie/err.c
> >>>> +++ b/drivers/pci/pcie/err.c
> >>>> @@ -203,6 +203,26 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
> >>>> pci_ers_result_t status = PCI_ERS_RESULT_CAN_RECOVER;
> >>>> struct pci_host_bridge *host = pci_find_host_bridge(dev->bus);
> >>>>
> >>>> + /*
> >>>> + * PCIe ports may include functionality beyond the standard
> >>>> + * extended port capabilities. This may present a need to log and
> >>>> + * handle errors not addressed in this driver. Examples are CXL
> >>>> + * root ports and CXL downstream switch ports using AER UIE to
> >>>> + * indicate CXL UCE RAS protocol errors.
> >>>> + */
> >>>> + if (type == PCI_EXP_TYPE_ROOT_PORT ||
> >>>> + type == PCI_EXP_TYPE_DOWNSTREAM) {
> >>>> + struct pci_driver *pdrv = dev->driver;
> >>>> +
> >>>> + if (pdrv && pdrv->err_handler &&
> >>>> + pdrv->err_handler->error_detected) {
> >>>> + const struct pci_error_handlers *err_handler;
> >>>> +
> >>>> + err_handler = pdrv->err_handler;
> >>>> + status = err_handler->error_detected(dev, state);
> >>>> + }
> >>>> + }
> >>>> +
> >>>
> >>> Would not a more appropriate place for this be pci_walk_bridge() where
> >>> the ->subordinate == NULL and these type-check cases are unified?
> >>
> >> It does. I can take a look at moving that.
> >
> > Has that already been handled in pci_walk_bridge?
> >
> > The function pci_walk_bridge() will call report_error_detected, where
> > the err handler will be called.
> > https://elixir.bootlin.com/linux/v6.10-rc6/source/drivers/pci/pcie/err.c#L80
> >
> > Fan
> >
>
> You would think so but the UCE handler was not called in my testing for the PCIe
> ports (RP,USP,DSP). The pci_walk_bridge() function has 2 cases:
> - If there is a subordinate/secondary bus then the callback is called for
> those downstream devices but not the port itself.
> - If there is no subordinate/secondary bus then the callback is invoked for the
> port itself.
>
> The function header comment may explain it better:
> /**
> * pci_walk_bridge - walk bridges potentially AER affected
> * @bridge: bridge which may be a Port, an RCEC, or an RCiEP
> * @cb: callback to be called for each device found
> * @userdata: arbitrary pointer to be passed to callback
> *
> * If the device provided is a bridge, walk the subordinate bus, including
> * any bridged devices on buses under this bus. Call the provided callback
> * on each device found.
> *
> * If the device provided has no subordinate bus, e.g., an RCEC or RCiEP,
> * call the callback on the device itself.
> */
>
> Regards,
> Terry

OK, interesting.
Btw, what is the "state" passed to pcie_do_recovery(...state...)?

Fan

>
> >>
> >> Regards,
> >> Terry