Re: [PATCH 1/1] PCI/AER: prevent pcie_do_fatal_recovery from using device after it is removed

[Sinan Kaya <okaya@kernel.org>]

On 8/21/2018 10:37 AM, Keith Busch wrote:
> On Tue, Aug 21, 2018 at 04:06:30PM +1000, Benjamin Herrenschmidt wrote:
>> On Tue, 2018-08-21 at 10:44 +0530, poza@codeaurora.org wrote:
>>>
>>> Ok Let me summarize the so far discussed things.
>>>
>>> It would be nice if we all (Bjorn, Keith, Ben, Sinan) can hold consensus
>>> on this.
>>>
>>> 1) Right now AER and DPC both calls pcie_do_fatal_recovery(), I majorly
>>> see DPC as error handling and recovery agent rather than being used for
>>> hotplug.
>>>      so in my opinion, both AER and DPC should have same error handling
>>> and recovery mechanism
>>
>> Yes.
>>
>>>      so if there is a way to figure out that in absence of pcihp, if DPC
>>> is being used to support hotplug then we fall back to original DPC
>>> mechanism (which is remove devices)
>>
>> Not exactly. If the presence detect change indicates it was a hotplug
>> event rather.
> 
> The actions associated with error recovery will trigger link state changes
> for a lot of existing hardware. PCIEHP currently does the same removal
> sequence for both link state change (DLLSC) and presence detect change
> (PDC) events.
> 
> It sounds like you want pciehp to do nothing on the DLLSC events that it
> currently handles, and instead do the board removal only on PDC.  If that
> is the case, is the desire to not remove devices downstream a permanently
> disabled link, or does that responsibility fall onto some other component?
> 

Looking at PDC is not enough. Hotplug driver handles both physical
removal as well as the link going down due to signal integrity issues today.

If the link went down because of a pending FATAL error, AER/DPC recovers
the link automatically. There is no need for hotplug to be involved in
fatal error work.

Hotplug driver needs to handle both physical removal as well as 
intermittent link down issues though.