Re: [PATCH 4/6] kselftest/arm64: Implement irritators for ZA and ZT

[Mark Rutland <mark.rutland@arm.com>]

On Wed, Oct 23, 2024 at 09:38:32PM +0100, Mark Brown wrote:
> Currently we don't use the irritator signal in our floating point stress
> tests so when we added ZA and ZT stress tests we didn't actually bother
> implementing any actual action in the handlers, we just counted the signal
> deliveries. In preparation for using the irritators let's implement them,
> just trivially SMSTOP and SMSTART to reset all bits in the register to 0.
> 
> Signed-off-by: Mark Brown <broonie@kernel.org>

Acked-by: Mark Rutland <mark.rutland@arm.com>

Mark.

> ---
>  tools/testing/selftests/arm64/fp/za-test.S | 12 ++++--------
>  tools/testing/selftests/arm64/fp/zt-test.S | 12 ++++--------
>  2 files changed, 8 insertions(+), 16 deletions(-)
> 
> diff --git a/tools/testing/selftests/arm64/fp/za-test.S b/tools/testing/selftests/arm64/fp/za-test.S
> index 1ee0ec36766d2bef92aff50a002813e76e22963c..f902e6ef9077bfa34fa7f85ce572ce3df4346789 100644
> --- a/tools/testing/selftests/arm64/fp/za-test.S
> +++ b/tools/testing/selftests/arm64/fp/za-test.S
> @@ -148,20 +148,16 @@ function check_za
>  	b	memcmp
>  endfunction
>  
> -// Any SME register modified here can cause corruption in the main
> -// thread -- but *only* the locations modified here.
> +// Modify the live SME register state, signal return will undo our changes
>  function irritator_handler
>  	// Increment the irritation signal count (x23):
>  	ldr	x0, [x2, #ucontext_regs + 8 * 23]
>  	add	x0, x0, #1
>  	str	x0, [x2, #ucontext_regs + 8 * 23]
>  
> -	// Corrupt some random ZA data
> -#if 0
> -	movi	v0.8b, #1
> -	movi	v9.16b, #2
> -	movi	v31.8b, #3
> -#endif
> +	// This will reset ZA to all bits 0
> +	smstop
> +	smstart
>  
>  	ret
>  endfunction
> diff --git a/tools/testing/selftests/arm64/fp/zt-test.S b/tools/testing/selftests/arm64/fp/zt-test.S
> index ade9c98abcdafc2755ef4796670566d99e919e5c..c96cb7c2ad4b406c54099fe3f73917259bd947e4 100644
> --- a/tools/testing/selftests/arm64/fp/zt-test.S
> +++ b/tools/testing/selftests/arm64/fp/zt-test.S
> @@ -117,20 +117,16 @@ function check_zt
>  	b	memcmp
>  endfunction
>  
> -// Any SME register modified here can cause corruption in the main
> -// thread -- but *only* the locations modified here.
> +// Modify the live SME register state, signal return will undo our changes
>  function irritator_handler
>  	// Increment the irritation signal count (x23):
>  	ldr	x0, [x2, #ucontext_regs + 8 * 23]
>  	add	x0, x0, #1
>  	str	x0, [x2, #ucontext_regs + 8 * 23]
>  
> -	// Corrupt some random ZT data
> -#if 0
> -	movi	v0.8b, #1
> -	movi	v9.16b, #2
> -	movi	v31.8b, #3
> -#endif
> +	// This will reset ZT to all bits 0
> +	smstop
> +	smstart
>  
>  	ret
>  endfunction
> 
> -- 
> 2.39.2
>