Re: [PATCH] PCI/AER: Cleanup AER error status registers on probing devices

[Bjorn Helgaas <bhelgaas@google.com>]

On Tue, Sep 01, 2015 at 08:14:41AM +0000, Izumi, Taku wrote:
> Dear Bjorn,
> 
>  Thanks for reviewing.
>  
> > Hello Taku-san,
> > 
> > On Wed, Aug 05, 2015 at 01:42:13AM +0900, Taku Izumi wrote:
> > > AER uncorrectable or correctable error might be recorded
> > > when power on devices. These errors can be ignored, so
> > > BIOS usually clean up these registers ahead of OS's scanning
> > > devices.
> > > However, in case of hot-plug PCIe devices, BIOS can't care.
> > 
> > What happens when we power down a device for suspend or because it's idle?
> > Can we get spurious AER errors when we power the device back up?  This
> > patch only covers the enumeration path, so we'd need to do more if it can
> > happen during suspend/resume.
> 
>   Our server only supports "suspend to disk". In that case,
>   BIOS cleans up those registers like boot-time.
>   So It seems that no troubles are previously reported other 
>   than hot-plug case.
> 
>   However, if box supports suspend-to-RAM, similar problem may happen.
>   It is true that that register clean-up should be done during suspend/resume
>   case. Should we cover during-suspend/resume case ?

Yes, I think so.  pci_restore_state() restores a lot of other
configuration; maybe it should do something with AER also.

There is a disturbing lack of symmetry between the boot/hot-add paths and
the resume-from-D3 path.  We're doing similar things, at least from the
hardware point of view, but the code is not similar at all.  It would be
nice if we could unify those somehow.

Bjorn