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

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Date:   Wed, 18 Jan 2017 15:53:24 -0700
From:   "Baicar, Tyler" <tbaicar@...eaurora.org>
To:     Will Deacon <will.deacon@....com>
Cc:     christoffer.dall@...aro.org, marc.zyngier@....com,
        pbonzini@...hat.com, rkrcmar@...hat.com, linux@...linux.org.uk,
        catalin.marinas@....com, rjw@...ysocki.net, lenb@...nel.org,
        matt@...eblueprint.co.uk, robert.moore@...el.com,
        lv.zheng@...el.com, nkaje@...eaurora.org, zjzhang@...eaurora.org,
        mark.rutland@....com, james.morse@....com,
        akpm@...ux-foundation.org, eun.taik.lee@...sung.com,
        sandeepa.s.prabhu@...il.com, labbott@...hat.com,
        shijie.huang@....com, rruigrok@...eaurora.org,
        paul.gortmaker@...driver.com, tn@...ihalf.com, fu.wei@...aro.org,
        rostedt@...dmis.org, bristot@...hat.com,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
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        astone@...hat.com, harba@...eaurora.org, hanjun.guo@...aro.org,
        john.garry@...wei.com, shiju.jose@...wei.com
Subject: Re: [PATCH V7 04/10] arm64: exception: handle Synchronous External
 Abort

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@...eaurora.org>
>>>> Signed-off-by: Jonathan (Zhixiong) Zhang <zjzhang@...eaurora.org>
>>>> Signed-off-by: Naveen Kaje <nkaje@...eaurora.org>
>>>> ---
>>>>   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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