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

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Message-ID: <668ef3a2.050a0220.96a0c.4f5c@mx.google.com>
Date: Wed, 10 Jul 2024 13:48:31 -0700
From: nifan.cxl@...il.com
To: Terry Bowman <Terry.Bowman@....com>
Cc: Dan Williams <dan.j.williams@...el.com>, ira.weiny@...el.com,
	dave@...olabs.net, dave.jiang@...el.com, alison.schofield@...el.com,
	ming4.li@...el.com, vishal.l.verma@...el.com,
	jim.harris@...sung.com, ilpo.jarvinen@...ux.intel.com,
	ardb@...nel.org, sathyanarayanan.kuppuswamy@...ux.intel.com,
	linux-cxl@...r.kernel.org, linux-kernel@...r.kernel.org,
	Yazen.Ghannam@....com, Robert.Richter@....com,
	Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org
Subject: Re: [RFC PATCH 1/9] PCI/AER: Update AER driver to call root port and
 downstream port UCE handlers

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@....com>
> >> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
> >> Cc: linux-pci@...r.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

> 
> Regards,
> Terry