Re: [PATCH] PCI: Fix order of device disablement on reset

[Keith Busch <kbusch@kernel.org>]

On Thu, Sep 17, 2026 at 02:38:42PM +0200, Lukas Wunner wrote:
> On Tue, Sep 15, 2026 at 10:08:32AM -0700, Farhan Ali wrote:
> > On 9/15/2026 6:35 AM, Lukas Wunner wrote:
> > > Riana reports an AER splat when issuing a Secondary Bus Reset through the
> > > "reset_subordinate" sysfs attribute:
> > > 
> > >    AER: Multiple Uncorrectable (Non-Fatal) error message received from 0000:01:00.0
> > >    PCIe Bus Error: severity=Uncorrectable (Non-Fatal), type=Transaction Layer, (Requester ID)
> > >      device [8086:e2ff] error status/mask=00100000/00400000
> > >      [20] UnsupReq               (First)
> > >    AER:   TLP Header: 0x40000001 0x0000000f 0x81190008 0x00000000
> > > 
> > > The Secondary Bus Reset is issued at the Root Port.  Underneath is a
> > > Switch with two Endpoints.  Riana has identified an ordering issue in
> > > pci_bus_save_and_disable_locked() as root cause of the AER splat:
> [...]
> > Since we are changing the order, maybe we should update comment for the
> > functions to reflect that. The change does make sense to me, but I am
> > curious why we didn't see this before?
> 
> We only enabled error reporting by default starting with v6.0 in 2022,
> cf. commit f26e58bf6f54.
> 
> And the reset_subordinate sysfs attribute only exists since v6.13 in 2025,
> cf. commit 2fa046449a82.
> 
> So it's relatively new functionality which apparently wasn't exercised
> heavily so far.

Yeah, we've used it to reset multi-function devices, but a deeper
topology like you described does look problematic here. Your proposal
makes the save state symmetrical with the restore side, so looks correct
to me.