Re: [PATCH V7 04/10] arm64: exception: handle Synchronous External Abort

[Baicar, Tyler]

On 1/17/2017 3:27 AM, Will Deacon wrote:
> On Mon, Jan 16, 2017 at 01:09:22PM -0700, Baicar, Tyler wrote:
> > On 1/16/2017 4:53 AM, Will Deacon wrote:
> > > On Thu, Jan 12, 2017 at 11:15:18AM -0700, Tyler Baicar wrote:
> > > > SEA exceptions are often caused by an uncorrected hardware
> > > > error, and are handled when data abort and instruction abort
> > > > exception classes have specific values for their Fault Status
> > > > Code.
> > > > When SEA occurs, before killing the process, go through
> > > > the handlers registered in the notification list.
> > > > Update fault_info[] with specific SEA faults so that the
> > > > new SEA handler is used.
> > > >
> > > > Signed-off-by: Tyler Baicar <tbaicar@xxxxxxxxxxxxxx>
> > > > Signed-off-by: Jonathan (Zhixiong) Zhang <zjzhang@xxxxxxxxxxxxxx>
> > > > Signed-off-by: Naveen Kaje <nkaje@xxxxxxxxxxxxxx>
> > > > ---
> > > >   arch/arm64/include/asm/system_misc.h | 13 ++++++++
> > > >   arch/arm64/mm/fault.c                | 58 +++++++++++++++++++++++++++++-------
> > > >   2 files changed, 61 insertions(+), 10 deletions(-)
> > > >
> > > > diff --git a/arch/arm64/include/asm/system_misc.h b/arch/arm64/include/asm/system_misc.h
> > > > index 57f110b..e7f3440 100644
> > > > --- a/arch/arm64/include/asm/system_misc.h
> > > > +++ b/arch/arm64/include/asm/system_misc.h
> > > > @@ -64,4 +64,17 @@ extern void (*arm_pm_restart)(enum reboot_mode reboot_mode, const char *cmd);
> > > >   #endif	/* __ASSEMBLY__ */
> > > > +/*
> > > > + * The functions below are used to register and unregister callbacks
> > > > + * that are to be invoked when a Synchronous External Abort (SEA)
> > > > + * occurs. An SEA is raised by certain fault status codes that have
> > > > + * either data or instruction abort as the exception class, and
> > > > + * callbacks may be registered to parse or handle such hardware errors.
> > > > + *
> > > > + * Registered callbacks are run in an interrupt/atomic context. They
> > > > + * are not allowed to block or sleep.
> > > > + */
> > > > +int register_sea_notifier(struct notifier_block *nb);
> > > > +void unregister_sea_notifier(struct notifier_block *nb);
> > > I still don't understand why you need notifiers for this. You register
> > > precisely one hook in the series.
> > I didn't see a response to my last comment on the previous series so I just
> > left it in for this series.
> > The notifier usage is consistent with the GHES code for SCI errors which are
> > also only used a single
> > time in the code. If you think making the call directly is a better option I
> > will remove the notifiers.
> Yes, please. It's easy to add the notifier infrastructure back if/when it's
> actually needed and I don't see why the low-level fault dispatching needs to
> be consistent with the GHES/SCI code.
>
> Will
Sounds good, I will remove the notifier in the next patchset.

Thanks,
Tyler

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