Re: [PATCH v4] PCI/AER: Enable error reporting for all ports

From: Keith Busch
Date: Fri Oct 19 2018 - 11:01:08 EST

On Thu, Oct 18, 2018 at 08:11:35PM -0500, Bjorn Helgaas wrote:
> On Thu, Oct 18, 2018 at 05:03:13PM -0600, Keith Busch wrote:
> > On Thu, Oct 18, 2018 at 03:53:58PM -0500, Bjorn Helgaas wrote:
> > > Change the AER service driver so it binds to *all* PCIe Ports,
> > > including Switch Upstream and Downstream Ports. Enable AER error
> > > reporting for all these Ports, but not for any children.
> >
> > I'm looking at this again and think enabling/disabling error
> > reporting for ports is the responsibility of the port driver, not
> > the AER service.
> That's an interesting idea. Can you expand on this a little more?
> Why is it the responsibility of the port driver?
> Do you think pci_enable_pcie_error_reporting() shouldn't be part of
> the AER service because it updates the Device Control register, which
> is in the PCIe Capability, not the AER Capability?
> What about pci_aer_clear_device_status(), which clears Device Status,
> which is also in the PCIe Capability?

I was comparing how other end device driver's enable this, and they all call
pci_enable_pcie_error_reporting() somewhere along their pci_driver->probe
path. With that in mind, are ports special compared to end devices for this
particular feature?

> > The following should do the same as this patch, but without making
> > AER driver handle non-root ports. The report enabling/disabling
> > functions are already stubbed for '!CONFIG_PCIE_AER' and have checks
> > for aer_cap and firmware first.
> If we thought we should enable error reporting *always*, regardless of
> whether the AER service is enabled, this would make perfect sense to
> me, and I might suggest doing it in an even more generic place like
> pci_configure_device() or pci_init_capabilities().

There are unfortunately still pci_driver instances that don't implement
the err_handler callbacks, and may cause problems if we enable error
reporting in the device when its driver isn't capable of reacting to them.

If it wasn't for that, I think it would make more sense to move this
responsibility from drivers to the pci core.

> But that doesn't seem like where you're headed. It seems like you
> still only want error reporting enabled when CONFIG_PCIEAR=y. If
> that's the case, it seems like doing it in portdrv only obfuscates the
> connection with AER. When CONFIG_PCIEAER is unset, the portdrv code
> *looks* like it's doing something but it's really not because of the
> #ifdef magic.

Right, but that's no different than every other Linux pci_driver. The
component that provides the pci_driver.err_handler should be responsible
for requesting to enable device error reporting, and that's provided by
the port driver, not AER.