[PATCH 12/14] powerpc/eeh: Add debugfs interface to run an EEH check

[Oliver O'Halloran]

On Tue, Sep 17, 2019 at 1:16 PM Sam Bobroff <sbobroff at linux.ibm.com> wrote:
>
> On Tue, Sep 03, 2019 at 08:16:03PM +1000, Oliver O'Halloran wrote:
> > Detecting an frozen EEH PE usually occurs when an MMIO load returns a 0xFFs
> > response. When performing EEH testing using the EEH error injection feature
> > available on some platforms there is no simple way to kick-off the kernel's
> > recovery process since any accesses from userspace (usually /dev/mem) will
> > bypass the MMIO helpers in the kernel which check if a 0xFF response is due
> > to an EEH freeze or not.
> >
> > If a device contains a 0xFF byte in it's config space it's possible to
> > trigger the recovery process via config space read from userspace, but this
> > is not a reliable method. If a driver is bound to the device an in use it
> > will frequently trigger the MMIO check, but this is also inconsistent.
> >
> > To solve these problems this patch adds a debugfs file called
> > "eeh_dev_check" which accepts a <domain>:<bus>:<dev>.<fn> string and runs
> > eeh_dev_check_failure() on it. This is the same check that's done when the
> > kernel gets a 0xFF result from an config or MMIO read with the added
> > benifit that it can be reliably triggered from userspace.
> >
> > Signed-off-by: Oliver O'Halloran <oohall at gmail.com>
>
> Looks good, and I tested it with the next patch and it seems to work.
>
> But I think you should make it clear that this does not work with
> the hardware "EEH error injection" facility accessible via debugfs in
> err_injct (that doesn't seem clear to me from the commit message).

It's not intended to be a separate mechanisms in the long term. I'm
planning on converting this interface to make use the platform defined
error injection mechanism once I can find how to use the PAPR ones
reliably. The idea is to use this as a generic "cause an EEH to happen
on this device" interface for userspace which we can use in test
scripts and the like.