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Message-ID: <05841914-183d-f2b6-37d8-4c34ea42b135@codeaurora.org>
Date: Fri, 6 Jan 2017 09:58:54 -0700
From: "Baicar, Tyler" <tbaicar@...eaurora.org>
To: Will Deacon <will.deacon@....com>
Cc: christoffer.dall@...aro.org, marc.zyngier@....com,
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Subject: Re: [PATCH V6 04/10] arm64: exception: handle Synchronous External
Abort
Hi Will,
On 1/4/2017 6:54 AM, Will Deacon wrote:
> On Wed, Dec 07, 2016 at 02:48:17PM -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..9040e1d 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_synchronous_ext_abort_notifier(struct notifier_block *nb);
>> +void unregister_synchronous_ext_abort_notifier(struct notifier_block *nb);
> I think that we may as well use the "SEA" acronym consistently in code,
> expanding it only for strings and comments, so these can be renamed to
> {register,unregister}_sea_notifier. That said, what is the use of having a
> notifier chain here as well as in the ghes code? If the ghes code is the
> only place to register a notifier, we may as well start simple and call that
> code directly, like we call handle_mm_fault directly for data aborts.
I originally used the acronym and got feedback to expand it, but I'll
revert back to just using the acronym.
Using a notifier here is consistent with the SCI error type in the GHES
code which is also only registered in
the GHES code. I can remove the notifier for SEA if you think making the
call directly is better here.
>> static const struct fault_info {
>> int (*fn)(unsigned long addr, unsigned int esr, struct pt_regs *regs);
>> int sig;
>> @@ -502,22 +540,22 @@ static const struct fault_info {
>> { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 1 permission fault" },
>> { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 2 permission fault" },
>> { do_page_fault, SIGSEGV, SEGV_ACCERR, "level 3 permission fault" },
>> - { do_bad, SIGBUS, 0, "synchronous external abort" },
>> + { do_synch_ext_abort, SIGBUS, 0, "synchronous external abort" },
> Again, just stick with do_sea for the function name...
>
>> { do_bad, SIGBUS, 0, "unknown 17" },
>> { do_bad, SIGBUS, 0, "unknown 18" },
>> { do_bad, SIGBUS, 0, "unknown 19" },
>> - { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" },
>> - { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" },
>> - { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" },
>> - { do_bad, SIGBUS, 0, "synchronous abort (translation table walk)" },
>> - { do_bad, SIGBUS, 0, "synchronous parity error" },
>> + { do_synch_ext_abort, SIGBUS, 0, "level 0 SEA (trans tbl walk)" },
> ... but there's no need to abbreviate "translation table walk" here. Long
> strings that run over 80 chars are fine. Similarly for "SEA".
I will expand this in the next patchset.
>> + { do_synch_ext_abort, SIGBUS, 0, "level 1 SEA (trans tbl walk)" },
>> + { do_synch_ext_abort, SIGBUS, 0, "level 2 SEA (trans tbl walk)" },
>> + { do_synch_ext_abort, SIGBUS, 0, "level 3 SEA (trans tbl walk)" },
>> + { do_synch_ext_abort, SIGBUS, 0, "synchronous parity or ECC err" },
>> { do_bad, SIGBUS, 0, "unknown 25" },
>> { do_bad, SIGBUS, 0, "unknown 26" },
>> { do_bad, SIGBUS, 0, "unknown 27" },
>> - { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk)" },
>> - { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk)" },
>> - { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk)" },
>> - { do_bad, SIGBUS, 0, "synchronous parity error (translation table walk)" },
>> + { do_synch_ext_abort, SIGBUS, 0, "level 0 synch parity error" },
>> + { do_synch_ext_abort, SIGBUS, 0, "level 1 synch parity error" },
>> + { do_synch_ext_abort, SIGBUS, 0, "level 2 synch parity error" },
>> + { do_synch_ext_abort, SIGBUS, 0, "level 3 synch parity error" },
> Please keep mention of "translation table walk", since we have exception
> levels too and it's confusing just saying "level n".
I will add them back in the next patchset.
Thanks,
Tyler
> Will
--
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