Re: [REGRESSION] Errors at reboot after 722e5f2b1eec

[Pingfan Liu <kernelfans@gmail.com>]

On Thu, Sep 13, 2018 at 10:15 PM Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
>
> On Thursday, September 13, 2018 12:03:36 PM CEST James Wang wrote:
> >  This is a multi-part message in MIME format.
> > --------------F5519E624D0AD1E3F7DDA019
> > Content-Type: text/plain; charset=utf-8
> > Content-Transfer-Encoding: 8bit
> >
> >
> >
> > On 09/11/2018 02:15 PM, Takashi Iwai wrote:
> > > On Tue, 11 Sep 2018 14:11:30 +0200,
> > > James Wang wrote:
> > >> I did try it from kernel : head
> > > OK, then the bug is present with 4.19-rc2, at least.
> > > Please check my test kernel later (it's still being built).
> > Hi folks,  I attach two log about 4.19-rc3 and 4.19-rc3+Rafeal suggestion.
>
> OK, no difference AFAICS.
>
> This means that the commit turned up by bisection simply uncovered an existing
> ordering issue, apparently between an IOMMU and its client (ie. it appears that
> the client is shut down after the IOMMU).
>
> This isn't limited to shutdown and you'd see the same issue on system-wide
> suspend/resume (in fact, the Pingfan Liu's patches make shutdown use the
> same device list that is used for system-wide PM).
>
> One way to mitigate such issues is to add a device link between the two
> devices in question to enforce the correct suspend/resume/shutdown ordering
> between them.
>
I found the iommu was at  " 0000:00:00.2", while  ohci-pci is at
0000:00:13.1. Hence ohci-pci should be shutdown before iommu. Not
familiar with AMD's iommu code, but I think there is no shutdown
interface exported to drivers/base. It is shutdown by platform code in
arch/x86. So I think there should be someone teared down the iotbl,
e.g. by invalidating pages, before the shutdown of ohci-pci. I wonder
whether adding a device link can fix this bug or not. (Forgive me if I
made a mistake, since I am ignorant in this field)

Thanks,
Pingfan