Re: [PATCH v3 1/1] PCI/ERR: Fix reset logic in pcie_do_recovery() call

[Kuppuswamy, Sathyanarayanan]

On 9/22/20 4:33 PM, Bjorn Helgaas wrote:
> On Tue, Sep 22, 2020 at 02:44:51PM -0700, Kuppuswamy, Sathyanarayanan wrote:
> > On 9/22/20 11:52 AM, Bjorn Helgaas wrote:
> > > On Fri, Jul 24, 2020 at 12:07:55PM -0700, sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx wrote:
> > > > From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
> > > >
> > > > Current pcie_do_recovery() implementation has following two issues:
> > >
> > > I'm having trouble parsing this out, probably just lack of my
> > > understanding...
> > >
> > > > 1. Fatal (DPC) error recovery is currently broken for non-hotplug
> > > > capable devices. Current fatal error recovery implementation relies
> > > > on PCIe hotplug (pciehp) handler for detaching and re-enumerating
> > > > the affected devices/drivers. pciehp handler listens for DLLSC state
> > > > changes and handles device/driver detachment on DLLSC_LINK_DOWN event
> > > > and re-enumeration on DLLSC_LINK_UP event. So when dealing with
> > > > non-hotplug capable devices, recovery code does not restore the state
> > > > of the affected devices correctly.
> > >
> > > Apparently in the hotplug case, something *does* restore the state of
> > > affected devices?
> >
> > Yes, in hotplug case, DLLSC state change handler takes over detachment
> > /cleanup and re-attachment of affected devices/drivers.
>
> Where does the restore happen here?  I.e., what function does this?

DLLSC link down event will remove affected devices/drivers. And link up event
will re-create all devices.

on DLLSC link down event
->pciehp_ist()
  ->pciehp_handle_presence_or_link_change()
    ->pciehp_disable_slot()
      ->__pciehp_disable_slot()
        ->remove_board()
          ->pciehp_unconfigure_device()

on DLLSC link up event
->pciehp_ist()
  ->pciehp_handle_presence_or_link_change()
    ->pciehp_enable_slot()
      ->__pciehp_enable_slot()
        ->board_added()
          ->pciehp_configure_device()

>

--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer