Re: [PATCH v1 1/1] PCI/ERR: Handle fatal error recovery for non-hotplug capable devices

[Kuppuswamy, Sathyanarayanan]

On 5/20/20 1:28 AM, Yicong Yang wrote:
> On 2020/5/7 11:32, sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx wrote:
> > From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
> >
> > If there are non-hotplug capable devices connected to a given
> > port, then during the fatal error recovery(triggered by DPC or
> > AER), after calling reset_link() function, we cannot rely on
> > hotplug handler to detach and re-enumerate the device drivers
> > in the affected bus. Instead, we will have to let the error
> > recovery handler call report_slot_reset() for all devices in
> > the bus to notify about the reset operation. Although this is
> > only required for non hot-plug capable devices, doing it for
> > hotplug capable devices should not affect the functionality.
> >
> > Along with above issue, this fix also applicable to following
> > issue.
> >
> > Commit 6d2c89441571 ("PCI/ERR: Update error status after
> > reset_link()") added support to store status of reset_link()
> > call. Although this fixed the error recovery issue observed if
> > the initial value of error status is PCI_ERS_RESULT_DISCONNECT
> > or PCI_ERS_RESULT_NO_AER_DRIVER, it also discarded the status
> > result from report_frozen_detected. This can cause a failure to
> > recover if _NEED_RESET is returned by report_frozen_detected and
> > report_slot_reset is not invoked.
> >
> > Such an event can be induced for testing purposes by reducing the
> > Max_Payload_Size of a PCIe bridge to less than that of a device
> > downstream from the bridge, and then initiating I/O through the
> > device, resulting in oversize transactions.  In the presence of DPC,
> > this results in a containment event and attempted reset and recovery
> > via pcie_do_recovery.  After 6d2c89441571 report_slot_reset is not
> > invoked, and the device does not recover.
> >
> > [original patch is from jay.vosburgh@xxxxxxxxxxxxx]
> > [original patch link https://lore.kernel.org/linux-pci/18609.1588812972@famine/]
> > Fixes: 6d2c89441571 ("PCI/ERR: Update error status after reset_link()")
> > Signed-off-by: Jay Vosburgh <jay.vosburgh@xxxxxxxxxxxxx>
> > Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
> > ---
> >   drivers/pci/pcie/err.c | 19 +++++++++++++++----
> >   1 file changed, 15 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/pci/pcie/err.c b/drivers/pci/pcie/err.c
> > index 14bb8f54723e..db80e1ecb2dc 100644
> > --- a/drivers/pci/pcie/err.c
> > +++ b/drivers/pci/pcie/err.c
> > @@ -165,13 +165,24 @@ pci_ers_result_t pcie_do_recovery(struct pci_dev *dev,
> >   	pci_dbg(dev, "broadcast error_detected message\n");
> >   	if (state == pci_channel_io_frozen) {
> >   		pci_walk_bus(bus, report_frozen_detected, &status);
> > -		status = reset_link(dev);
> > -		if (status != PCI_ERS_RESULT_RECOVERED) {
> > +		status = PCI_ERS_RESULT_NEED_RESET;
> > +	} else {
> > +		pci_walk_bus(bus, report_normal_detected, &status);
> > +	}
> > +
> > +	if (status == PCI_ERS_RESULT_NEED_RESET) {
> > +		if (reset_link) {
> > +			if (reset_link(dev) != PCI_ERS_RESULT_RECOVERED)
>
> we'll call reset_link() only if link is frozen. so it may have problem here.
you mean before this change right?
After this change, reset_link() will be called as long as status is
PCI_ERS_RESULT_NEED_RESET.
> Thanks,
> Yicong
>
>
> > +				status = PCI_ERS_RESULT_DISCONNECT;
> > +		} else {
> > +			if (pci_bus_error_reset(dev))
> > +				status = PCI_ERS_RESULT_DISCONNECT;
> > +		}
> > +
> > +		if (status == PCI_ERS_RESULT_DISCONNECT) {
> >   			pci_warn(dev, "link reset failed\n");
> >   			goto failed;
> >   		}
> > -	} else {
> > -		pci_walk_bus(bus, report_normal_detected, &status);
> >   	}
> >   
> >   	if (status == PCI_ERS_RESULT_CAN_RECOVER) {