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

[Hanjun Guo]

Hi Harb,

On 2016/10/20 0:59, Abdulhamid, Harb wrote:
> On 10/18/2016 8:44 AM, Hanjun Guo wrote:
>> Hi Tyler,
>>
>> 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.
>> Does this SEA is replayed by the firmware (firmware first handling)
>> or directly triggered by the hardware when error is happened?
> Architecturally, an SEA must be synchronous and *precise*, so if you
> take an SEA on a particular load instruction, firmware/hardware should
> not be corrupting the context/state of the PE to allow software to
> determine which thread/process encountered the abort.  GHES error status

That's my concern too, and that's why I raised my question :)

> block will be expose to software with information about the type,
> severity, physical address impacted.
>
> Generally the error status block is populated by firmware.  However, as
> long as the above requirement is met, I don't think the spec precludes
> error status block being populated by hardware.  Those details must be
> completely transparent to software.
>
> Finally, to answer your more specific question:  If the implementation
> of firmware-first involves trapping the SEA in EL3 to do some firmware
> first handling, firmware must maintain the context of the offending ELx,
> generate an error record, and then "replay" the exception to normal
> (non-secure) software at the appropriate vector base address.
>

Thank you for your answer, it clears my confusion now, I will try something
similar on ARM64 platform, will get back to you if I get blocks.

Thanks
Hanjun