Re: [PATCH V3 05/10] acpi: apei: handle SEA notification type for ARMv8

[Abdulhamid, Harb]

On 10/18/2016 9:04 AM, Hanjun Guo wrote:
> On 2016/10/8 5:31, Tyler Baicar wrote:
>> ARM APEI extension proposal added SEA (Synchrounous External
>> Abort) notification type for ARMv8.
>> Add a new GHES error source handling function for SEA. If an error
>> source's notification type is SEA, then this function can be registered
>> into the SEA exception handler. That way GHES will parse and report
>> SEA exceptions when they occur.
>>
>> Signed-off-by: Jonathan (Zhixiong) Zhang <zjzhang@xxxxxxxxxxxxxx>
>> Signed-off-by: Tyler Baicar <tbaicar@xxxxxxxxxxxxxx>
>> Signed-off-by: Naveen Kaje <nkaje@xxxxxxxxxxxxxx>
>> ---
>>  arch/arm64/Kconfig        |  1 +
>>  drivers/acpi/apei/Kconfig | 15 +++++++++
>>  drivers/acpi/apei/ghes.c  | 83
>> +++++++++++++++++++++++++++++++++++++++++++++++
>>  3 files changed, 99 insertions(+)
>>
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index b380c87..ae34349 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -53,6 +53,7 @@ config ARM64
>>      select HANDLE_DOMAIN_IRQ
>>      select HARDIRQS_SW_RESEND
>>      select HAVE_ACPI_APEI if (ACPI && EFI)
>> +    select HAVE_ACPI_APEI_SEA if (ACPI && EFI)
>>      select HAVE_ALIGNED_STRUCT_PAGE if SLUB
>>      select HAVE_ARCH_AUDITSYSCALL
>>      select HAVE_ARCH_BITREVERSE
>> diff --git a/drivers/acpi/apei/Kconfig b/drivers/acpi/apei/Kconfig
>> index b0140c8..fb99c1c 100644
>> --- a/drivers/acpi/apei/Kconfig
>> +++ b/drivers/acpi/apei/Kconfig
>> @@ -4,6 +4,21 @@ config HAVE_ACPI_APEI
>>  config HAVE_ACPI_APEI_NMI
>>      bool
>>
>> +config HAVE_ACPI_APEI_SEA
>> +    bool "APEI Synchronous External Abort logging/recovering support"
>> +    depends on ARM64
>> +    help
>> +      This option should be enabled if the system supports
>> +      firmware first handling of SEA (Synchronous External Abort).
>> +      SEA happens with certain faults of data abort or instruction
>> +      abort synchronous exceptions on ARMv8 systems. If a system
>> +      supports firmware first handling of SEA, the platform analyzes
>> +      and handles hardware error notifications with SEA, and it may then
>> +      form a HW error record for the OS to parse and handle. This
>> +      option allows the OS to look for such HW error record, and
>> +      take appropriate action.
> 
> OK, I can see that it's firmware first handling, so it's triggered
> by firmware to me, correct me if I'm wrong.

Not exactly... the exception itself is *initially* triggered by the
processor itself (e.g. ECC error on a particular load causes a data
abort), but then may be intercepted by firmware (e.g. EL3) to generate
the error record and then be *replayed* back to software (e.g. jump to
appropriate EL and vector that originally caused the exception).

The reason we use the term "platform" here is because platform can be
hardware/firmware, and this can be implemented in different ways
depending on the preference of the platform vendor.  This is consistent
with the language in the UEFI/ACPI spec when describing the "thing" that
is not normal software (i.e. OS/Hypervisor).

> 
> [...]
>>  #ifdef CONFIG_HAVE_ACPI_APEI_NMI
>>  /*
>>   * printk is not safe in NMI context.  So in NMI handler, we allocate
>> @@ -1023,6 +1083,14 @@ static int ghes_probe(struct platform_device
>> *ghes_dev)
>>      case ACPI_HEST_NOTIFY_EXTERNAL:
>>      case ACPI_HEST_NOTIFY_SCI:
>>          break;
>> +    case ACPI_HEST_NOTIFY_SEA:
>> +        if (!IS_ENABLED(CONFIG_HAVE_ACPI_APEI_SEA)) {
>> +            pr_warn(GHES_PFX "Generic hardware error source: %d
>> notified via SEA is not supported\n",
>> +                generic->header.source_id);
>> +            rc = -ENOTSUPP;
>> +            goto err;
>> +        }
>> +        break;
>>      case ACPI_HEST_NOTIFY_NMI:
>>          if (!IS_ENABLED(CONFIG_HAVE_ACPI_APEI_NMI)) {
>>              pr_warn(GHES_PFX "Generic hardware error source: %d
>> notified via NMI interrupt is not supported!\n",
>> @@ -1034,6 +1102,13 @@ static int ghes_probe(struct platform_device
>> *ghes_dev)
>>          pr_warning(GHES_PFX "Generic hardware error source: %d
>> notified via local interrupt is not supported!\n",
>>                 generic->header.source_id);
>>          goto err;
>> +    case ACPI_HEST_NOTIFY_GPIO:
>> +    case ACPI_HEST_NOTIFY_SEI:
>> +    case ACPI_HEST_NOTIFY_GSIV:
>> +        pr_warn(GHES_PFX "Generic hardware error source: %d notified
>> via notification type %u is not supported\n",
>> +            generic->header.source_id, generic->header.source_id);
> 
> Hmm, some platform may trigger a interrupt to OS for firmware handling
> and it's in the ACPI 6.1 spec, is it a limitation now, or we need to
> add code later to support it?

On the current platforms we know of, we only leverage "emulated SCI",
which essentially maps to a GPIO interrupt (via ACPI event - mapped to
particular GPIO).  We will need to add support for other options
available in the spec (e.g. GSIV and SEI) later as platforms that use
those notification types become available.

Thanks,
--Harb
-- 
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