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Subject: Re: [PATCH 1/1] PCI/AER: prevent pcie_do_fatal_recovery from using
 device after it is removed
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Sinan Kaya <okaya@kernel.org>, Keith Busch <keith.busch@intel.com>
Cc: poza@codeaurora.org, Bjorn Helgaas <helgaas@kernel.org>,
        Thomas Tai
	 <thomas.tai@oracle.com>, bhelgaas@google.com,
        linux-pci@vger.kernel.org, linux-pci-owner@vger.kernel.org,
        Sam Bobroff <sam.bobroff@au1.ibm.com>
Date: Tue, 21 Aug 2018 08:04:46 +1000
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On Mon, 2018-08-20 at 18:02 -0400, Sinan Kaya wrote:
> On 8/20/2018 5:53 PM, Benjamin Herrenschmidt wrote:
> > > > Hotplug driver removes the devices on link down events and re-enumerates
> > > > on insertion.
> > > > 
> > > > I am trying to separate fatal error handling from hotplug.
> > > 
> > > I'll try to take a look. We can't always count on pciehp to do the
> > > removal when a removal occurs, though. The PCIe specification contains
> > > an implementation note that DPC may be used in place of hotplug surprise.
> > 
> > Can't you use the presence detect to differenciate ?
> > 
> > Also, I don't have the specs at hand right now, but does the hotplug
> > brigde have a way to "latch' the change in presence detect so we can
> > see if it has transitioned even if it's back on ?
> 
> There is only presence detect change and link layer change. No actual
> state information.

It does latch that it has changed tho right ? So if presence detect
hasn't changed, we can assume it's an error and not an unplug ?

We could discriminate that way to reduce the risk of doing a recovery
without unbind on something that was actually removed and replaced.

Cheers,
Ben.