[PATCH v6 7/7] kselftest/arm64: Add HWCAP test for FEAT_{LS64, LS64_V}

[Arnd Bergmann]

On Mon, Oct 27, 2025, at 03:50, Zhou Wang wrote:
> On 2025/10/25 18:06, Zhou Wang wrote:
>> On 2025/10/25 0:18, Arnd Bergmann wrote:
>>> On Fri, Oct 24, 2025, at 11:08, Zhou Wang wrote:
>>>
>>> Is ST64BV expected to cause SIGBUS here, or should it return the
>>> 0xffffffffffffffff output to indicate an unsupported memory area?
>> 
>> I think it should return 0xffffffffffffffff without an exception,
>
> My understanding above is wrong.
>
> As mentioned in C3.2.6 of ARM spec L.b:
>
> 1. "When the instructions access a memory type that is not one of the following,
>    a data abort for unsupported Exclusive or atomic access is generated"
>
> 2. "If the target memory location does not support the ST64BV or ST64BV0
>    instructions, then the register specified by <Xs> is set to 
> 0xFFFFFFFF_FFFFFFFF"
>
> Here the test code is the first case, so a fault should be triggered.

I see, my mistake.

     Arnd