Re: [PATCH v7 2/5] PCI/DPC: Run recovery on device that detected the error

[Shuai Xue]

On 2/27/26 6:47 PM, Lukas Wunner wrote:
> On Fri, Feb 27, 2026 at 04:28:59PM +0800, Shuai Xue wrote:
> > On 2/7/26 3:48 PM, Shuai Xue wrote:
> > > Regarding pci_restore_state() in slot_reset(): I see now that it does
> > > call pci_aer_clear_status(dev) (at line 1844 in pci.c), which will
> > > clear the AER Status registers. So if we walk the hierarchy after
> > > the slot_reset callbacks, the error bits accumulated during DPC will
> > > already be cleared.
> > >
> > > To avoid losing those errors, I think the walk should happen after
> > > dpc_reset_link() succeeds but *before* pcie_do_recovery() invokes the
> > > slot_reset callbacks. That way, we can capture the AER Status bits
> > > before pci_restore_state() clears them.
> > >
> > > Does that sound like the right approach, or would you prefer a
> > > different placement?
>
> The problem is that if the hierarchy that was reset is deeper than
> one level, you first need to call pci_restore_state() on all the
> PCIe Upstream and Downstream Ports that were reset before you can
> access the Endpoints at the bottom of the hierarchy.
>
> E.g. if DPC occurs at a Root Port with multiple nested PCIe switches
> below, the Endpoints at the "leafs" of that tree are only accessible
> once Config Space has been restored at all the PCIe switches
> in-between the Endpoints and the DPC-capable Root Port.
>
> Hence your proposal unfortunately won't work.
>
> I think the solution is to move pci_aer_clear_status() out of
> pci_restore_state() into the callers that actually need it.
> But that requires going through every single caller.
> I've begun doing that last week and am about 60% done.
>
> Once pci_restore_state() no longer clears the error bits, we can
> report and clear them after the "report_slot_reset" stage (which
> is where drivers call pci_restore_state()).
>
> I've also changed my mind and I think reporting and clearing
> the error bits *could* happen in pcie_do_recovery() even if it
> were used for EEH and s390 because those platforms may plug in
> AER-capable devices as well and so we do need to clear the bits
> regardless of the error recovery mechanism used.
>
> Let me get back to you once I've gone through all the callers of
> pci_restore_state().  Please be patient.

Sure, glad to hear you have been working on that.


Thanks.
SHuai