[PATCH 05/18] arm64: fpsimd: Fold sve_init_regs() into do_sve_acc()

[Vladimir Murzin]

On 5/21/26 14:25, Mark Rutland wrote:
> For historical reasons, do_sve_acc() is structurally different from
> do_sme_acc(), and the logic to convert the task from FPSIMD to SVE is
> out-of-line in sve_init_regs(). We only use sve_init_regs() within
> do_sme_acc(), so it's not necessary for this to be a separate function.
> 
> Fold sve_init_regs() into do_sve_acc(), and simplify the associated
> comments. This makes do_sve_acc() structurally similar to do_sme_acc(),
> making it easier to see similarities and differences.
> 
> There should be no functional change as a result of this patch.
> 
> Signed-off-by: Mark Rutland <mark.rutland at arm.com>
> Cc: Catalin Marinas <catalin.marinas at arm.com>
> Cc: Fuad Tabba <tabba at google.com>
> Cc: James Morse <james.morse at arm.com>
> Cc: Marc Zyngier <maz at kernel.org>
> Cc: Mark Brown <broonie at kernel.org>
> Cc: Oliver Upton <oupton at kernel.org>
> Cc: Will Deacon <will at kernel.org>
> ---
>  arch/arm64/kernel/fpsimd.c | 48 ++++++++++++++------------------------
>  1 file changed, 17 insertions(+), 31 deletions(-)
> 
> diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
> index 60a45d600b460..a8395cb303344 100644
> --- a/arch/arm64/kernel/fpsimd.c
> +++ b/arch/arm64/kernel/fpsimd.c
> @@ -1293,31 +1293,6 @@ void sme_suspend_exit(void)
>  
>  #endif /* CONFIG_ARM64_SME */
>  
> -static void sve_init_regs(void)
> -{
> -	/*
> -	 * Convert the FPSIMD state to SVE, zeroing all the state that
> -	 * is not shared with FPSIMD. If (as is likely) the current
> -	 * state is live in the registers then do this there and
> -	 * update our metadata for the current task including
> -	 * disabling the trap, otherwise update our in-memory copy.
> -	 * We are guaranteed to not be in streaming mode, we can only
> -	 * take a SVE trap when not in streaming mode and we can't be
> -	 * in streaming mode when taking a SME trap.
> -	 */
> -	if (!test_thread_flag(TIF_FOREIGN_FPSTATE)) {
> -		unsigned long vq_minus_one =
> -			sve_vq_from_vl(task_get_sve_vl(current)) - 1;
> -		sve_set_vq(vq_minus_one);
> -		sve_flush_live(true, vq_minus_one);
> -		fpsimd_bind_task_to_cpu();
> -	} else {
> -		fpsimd_to_sve(current);
> -		current->thread.fp_type = FP_STATE_SVE;
> -		fpsimd_flush_task_state(current);
> -	}
> -}
> -
>  /*
>   * Trapped SVE access
>   *
> @@ -1349,13 +1324,24 @@ void do_sve_acc(unsigned long esr, struct pt_regs *regs)
>  		WARN_ON(1); /* SVE access shouldn't have trapped */
>  
>  	/*
> -	 * Even if the task can have used streaming mode we can only
> -	 * generate SVE access traps in normal SVE mode and
> -	 * transitioning out of streaming mode may discard any
> -	 * streaming mode state.  Always clear the high bits to avoid
> -	 * any potential errors tracking what is properly initialised.
> +	 * Convert the FPSIMD state to SVE. Stale SVE state can be present in
> +	 * registers or memory, so we must zero all state that is not shared
> +	 * with FPSIMD.
> +	 *
> +	 * SVE traps cannot be taken from streaming mode, so there cannot be
> +	 * any effective streaming mode SVE state.
>  	 */
> -	sve_init_regs();
> +	if (!test_thread_flag(TIF_FOREIGN_FPSTATE)) {
> +		unsigned long vq_minus_one =
> +			sve_vq_from_vl(task_get_sve_vl(current)) - 1;
> +		sve_set_vq(vq_minus_one);
> +		sve_flush_live(true, vq_minus_one);
> +		fpsimd_bind_task_to_cpu();
> +	} else {
> +		fpsimd_to_sve(current);
> +		current->thread.fp_type = FP_STATE_SVE;
> +		fpsimd_flush_task_state(current);
> +	}
>  
>  	put_cpu_fpsimd_context();
>  }
> -- 2.30.2
> 

FWIW,

Reviewed-by: Vladimir Murzin <vladimir.murzin at arm.com>