linux-kernel - Re: [PATCH 1/6] kselftest/arm64: Correct misleading comments on fp-stress irritators

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Message-ID: <ZytTDJOfFaynG1rp@J2N7QTR9R3>
Date: Wed, 6 Nov 2024 11:29:16 +0000
From: Mark Rutland <mark.rutland@....com>
To: Mark Brown <broonie@...nel.org>
Cc: Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>, Shuah Khan <shuah@...nel.org>,
	linux-arm-kernel@...ts.infradead.org,
	linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6] kselftest/arm64: Correct misleading comments on
 fp-stress irritators

On Wed, Oct 23, 2024 at 09:38:29PM +0100, Mark Brown wrote:
> The comments in the handlers for the irritator signal in the test threads
> for fp-stress suggest that the irritator will corrupt the register state
> observed by the main thread but this is not the case, instead the FPSIMD
> and SVE irritators (which are the only ones that are implemented) modify
> the current register state which is expected to be overwritten on return
> from the handler by the saved register state. Update the comment to reflect
> what the handler is actually doing.
> 
> Signed-off-by: Mark Brown <broonie@...nel.org>

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

Mark.

> ---
>  tools/testing/selftests/arm64/fp/fpsimd-test.S | 3 +--
>  tools/testing/selftests/arm64/fp/sve-test.S    | 3 +--
>  2 files changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/testing/selftests/arm64/fp/fpsimd-test.S b/tools/testing/selftests/arm64/fp/fpsimd-test.S
> index 8b960d01ed2e0ef516893b68794078ddf8c01e1f..bdfb7cf2e4ec175fda62c1c2f38c6ebb1a1c48bf 100644
> --- a/tools/testing/selftests/arm64/fp/fpsimd-test.S
> +++ b/tools/testing/selftests/arm64/fp/fpsimd-test.S
> @@ -134,8 +134,7 @@ function check_vreg
>  	b	memcmp
>  endfunction
>  
> -// Any SVE register modified here can cause corruption in the main
> -// thread -- but *only* the registers modified here.
> +// Modify live register state, the signal return will undo our changes
>  function irritator_handler
>  	// Increment the irritation signal count (x23):
>  	ldr	x0, [x2, #ucontext_regs + 8 * 23]
> diff --git a/tools/testing/selftests/arm64/fp/sve-test.S b/tools/testing/selftests/arm64/fp/sve-test.S
> index fff60e2a25addfd4850ef71aa3cf6535ac880ffd..e3c0d585684df29723a49265f3df6d23817498c7 100644
> --- a/tools/testing/selftests/arm64/fp/sve-test.S
> +++ b/tools/testing/selftests/arm64/fp/sve-test.S
> @@ -291,8 +291,7 @@ function check_ffr
>  #endif
>  endfunction
>  
> -// Any SVE register modified here can cause corruption in the main
> -// thread -- but *only* the registers modified here.
> +// Modify live register state, the signal return will undo our changes
>  function irritator_handler
>  	// Increment the irritation signal count (x23):
>  	ldr	x0, [x2, #ucontext_regs + 8 * 23]
> 
> -- 
> 2.39.2
>