Re: [RFC PATCH 4/9] PCI/AER: Extend AER error handling to RCECs

[Sean V Kelley]

On 27 Jul 2020, at 7:04, Jonathan Cameron wrote:

> On Fri, 24 Jul 2020 10:22:18 -0700
> Sean V Kelley <sean.v.kelley@xxxxxxxxx> wrote:
>
> > From: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
> >
> > Currently the kernel does not handle AER errors for Root Complex 
> > integrated
> > End Points (RCiEPs)[0]. These devices sit on a root bus within the 
> > Root Complex
> > (RC). AER handling is performed by a Root Complex Event Collector 
> > (RCEC) [1]
> > which is a effectively a type of RCiEP on the same root bus.
> >
> > For an RCEC (technically not a Bridge), error messages "received" 
> > from
> > associated RCiEPs must be enabled for "transmission" in order to 
> > cause a
> > System Error via the Root Control register or (when the Advanced 
> > Error
> > Reporting Capability is present) reporting via the Root Error Command
> > register and logging in the Root Error Status register and Error 
> > Source
> > Identification register.
> >
> > In addition to the defined OS level handling of the reset flow for 
> > the
> > associated RCiEPs of an RCEC, it is possible to also have a firmware 
> > first
> > model. In that case there is no need to take any actions on the RCEC 
> > because
> > the firmware is responsible for them. This is true where APEI [2] is 
> > used
> > to report the AER errors via a GHES[v2] HEST entry [3] and relevant
> > AER CPER record [4] and Firmware First handling is in use.
> >
> > We effectively end up with two different types of discovery for
> > purposes of handling AER errors:
> >
> > 1) Normal bus walk - we pass the downstream port above a bus to which
> > the device is attached and it walks everything below that point.
> >
> > 2) An RCiEP with no visible association with an RCEC as there is no 
> > need to
> > walk devices. In that case, the flow is to just call the callbacks 
> > for the actual
> > device.
> >
> > A new walk function, similar to pci_bus_walk is provided that takes a 
> > pci_dev
> > instead of a bus. If that dev corresponds to a downstream port it 
> > will walk
> > the subordinate bus of that downstream port. If the dev does not then 
> > it
> > will call the function on that device alone.
> >
> > [0] ACPI PCI Express Base Specification 5.0-1 1.3.2.3 Root Complex 
> > Integrated
> >     Endpoint Rules.
> > [1] ACPI PCI Express Base Specification 5.0-1 6.2 Error Signalling 
> > and Logging
> > [2] ACPI Specification 6.3 Chapter 18 ACPI Platform Error Interface 
> > (APEI)
> > [3] ACPI Specification 6.3 18.2.3.7 Generic Hardware Error Source
> > [4] UEFI Specification 2.8, N.2.7 PCI Express Error Section
> >
> > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
> > Signed-off-by: Sean V Kelley <sean.v.kelley@xxxxxxxxx>
> > ---
> ...
>
>
> >  	pci_dbg(dev, "broadcast resume message\n");
> > -	pci_walk_bus(bus, report_resume, &status);
> > +	pci_walk_dev_affected(dev, report_resume, &status);
> >
> > -	pci_aer_clear_device_status(dev);
> > -	pci_aer_clear_nonfatal_status(dev);
>
> This code had changed a little in Bjorn's pci/next branch so do a 
> rebase on that
> before v2.

Will ensure rebase includes pci/next.

Thanks,

Sean

> > +	if ((pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT ||
> > +	     pci_pcie_type(dev) == PCI_EXP_TYPE_DOWNSTREAM ||
> > +	     pci_pcie_type(dev) == PCI_EXP_TYPE_RC_EC)) {
> > +		pci_aer_clear_device_status(dev);
> > +		pci_aer_clear_nonfatal_status(dev);
> > +	}
> >  	pci_info(dev, "device recovery successful\n");
> >  	return status;