Re: [PATCH 2/2] arm64: sleep: dedup the sleep_save_stash slot lookup

[Will Deacon <will@kernel.org>]

On Sun, Jul 05, 2026 at 07:23:31PM +0000, Bradley Morgan wrote:
> Both __cpu_suspend_enter() and _cpu_resume() open code the same MPIDR
> hash lookup. Factor it into a get_sleep_stash_slot macro.
> 
> Signed-off-by: Bradley Morgan <include@grrlz.net>
> ---
>  arch/arm64/kernel/sleep.S | 55 +++++++++++++++++++++------------------
>  1 file changed, 30 insertions(+), 25 deletions(-)
> 
> diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S
> index e112b8537f10..8820a131aef7 100644
> --- a/arch/arm64/kernel/sleep.S
> +++ b/arch/arm64/kernel/sleep.S
> @@ -64,6 +64,31 @@
>  	lsr	\mask ,\mask, \rs3
>  	orr	\dst, \dst, \mask		// dst|=(aff3>>rs3)
>  	.endm
> +
> +/*
> + * Compute the address of the current CPU's entry in sleep_save_stash,
> + * i.e. &sleep_save_stash[hash(MPIDR_EL1)].
> + *
> + * @slot: output register
> + *
> + * Clobbers: x2 - x8
> + */
> +	.macro get_sleep_stash_slot slot
> +	mpidr_hash_assert_distinct \slot, x2
> +	mrs	x3, mpidr_el1
> +	adr_l	x2, mpidr_hash
> +	ldr	x8, [x2, #MPIDR_HASH_MASK]
> +	/*
> +	 * Following code relies on the struct mpidr_hash
> +	 * members size.
> +	 */
> +	ldp	w4, w5, [x2, #MPIDR_HASH_SHIFTS]
> +	ldp	w6, w7, [x2, #(MPIDR_HASH_SHIFTS + 8)]
> +	compute_mpidr_hash x2, x4, x5, x6, x7, x3, x8
> +	ldr_l	\slot, sleep_save_stash
> +	add	\slot, \slot, x2, lsl #3
> +	.endm

I think this would now be the only user of compute_mpidr_hash, so it's
probably better to inline that macro here and then we don't need to
bother with mpidr_hash_assert_distinct at all (i.e. your first patch
isn't needed).

Will