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

On Mon, Oct 27, 2025, at 03:50, Zhou Wang wrote:

On 2025/10/25 18:06, Zhou Wang wrote:

quoted

On 2025/10/25 0:18, Arnd Bergmann wrote:

quoted

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