On Mon, 2018-08-20 at 18:56 +0530, poza@xxxxxxxxxxxxxx wrote: > Hi Ben, > > I get the idea and get your points. and when I started implementation of > this, I did ask these questions to myself. > but then we all fell aligned to what DPC was doing, because thats how > the driver was dealing with ERR_FATAL. > > I can put together a patch adhering to the idea, and modify err.c. > let me know if you are okay with that. > I have both DPC and AER capable root port, so I can easily validate the > changes as we improve upon this. > > besides We have to come to some common ground on policy. > 1) if device driver dictates the reset we should agree to do SBR. > (irrespective of the type of error) It's not just "the driver dictates the reset". It's a combination of all agents. Either the driver or the framework, *both* can request a reset. Also if you have multiple devices involved (for example multiple functions), then any of the drivers can request the reset. > 2) under what circumstances framework will impose the reset, even if > device driver did not ! Well ERR_FATAL typically would be one. Make it an argument to the framework, it's possible that EEH might always do, I have to look into it. > probably changes might be simpler; although it will require to exercise > some tests cases for both DPC and AER. > let me know if anything I missed here, but let me attempt to make patch > and we can go form there. > > Let me know you opinion. I agree. Hopefully Sam will have a chance to chime in (he's caught up with something else at the moment) as well. Cheers, Ben. > Regards, > Oza. > > > > > > Also I am very much interested in knowing original intention of DPC > > > driver to unplug/plug devices, > > > all I remember in some conversation was: > > > hotplug capable bridge might have see devices changed, so it is safer > > > to > > > remove/unplug the devices and during which .shutdown methods of driver > > > is called, in case of ERR_FATAL. > > > > The device being "swapped" during an error recovery operation is ... > > unlikely. Do the bridges have a way to latch that the presence detect > > changed ? > > > > > although DPC is HW recovery while AER is sw recovery both should > > > fundamentally act in the same way as far as device drivers callbacks > > > are > > > concerned. > > > (again I really dont know real motivation behind this) > > > > The main problem with unplug/replug (as I mentioned earlier) is that it > > just does NOT work for storage controllers (or similar type of > > devices). The links between the storage controller and the mounted > > filesystems is lost permanently, you'll most likely have to reboot the > > machine. > > > > With our current EEH implementation we can successfully recover from > > fatal errors with the storage controller by resetting it. > > > > Finally as for PERST vs. Hot Reset, this is an implementation detail. > > Not all our platforms can control PERST on all devices either, we > > generally prefer PERST as it provides a more reliable reset mechanism > > in practice (talking from experience) but will fallback to hot reset. > > > > Cheers, > > Ben. > > > > > > > > Regards, > > > Oza. > > > > > > > - Figure out what hooks might be needed to be able to plumb EEH into > > > > it, possibly removing a bunch of crap in arch/powerpc (yay !) > > > > > > > > I don't think having a webex will be that practical with the timezones > > > > involved. I'm trying to get approval to go to Plumbers in which case we > > > > could setup a BOF but I have no guarantee at this point that I can make > > > > it happen. > > > > > > > > So let's try using email as much possible for now. > > > > > > > > Cheers, > > > > Ben.
