[PATCH v2 11/16] powerpc/64: pcpu setup avoid reading mmu_linear_psize on 64e or radix

[Christophe Leroy]

Le 21/10/2021 à 05:54, Nicholas Piggin a écrit :
> Radix never sets mmu_linear_psize so it's always 4K, which causes pcpu
> atom_size to always be PAGE_SIZE. 64e sets it to 1GB always.
> 
> Make paths for these platforms to be explicit about what value they set
> atom_size to.
> 
> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
> ---
>   arch/powerpc/kernel/setup_64.c | 21 +++++++++++++++------
>   1 file changed, 15 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
> index eaa79a0996d1..7d4bcbc3124e 100644
> --- a/arch/powerpc/kernel/setup_64.c
> +++ b/arch/powerpc/kernel/setup_64.c
> @@ -880,14 +880,23 @@ void __init setup_per_cpu_areas(void)
>   	int rc = -EINVAL;
>   
>   	/*
> -	 * Linear mapping is one of 4K, 1M and 16M.  For 4K, no need
> -	 * to group units.  For larger mappings, use 1M atom which
> -	 * should be large enough to contain a number of units.
> +	 * BookE and BookS radix are historical values and should be revisited.
>   	 */
> -	if (mmu_linear_psize == MMU_PAGE_4K)
> -		atom_size = PAGE_SIZE;
> -	else
> +	if (IS_ENABLED(CONFIG_PPC_BOOK3E)) {
>   		atom_size = 1 << 20;
> +	} else if (radix_enabled()) {
> +		atom_size = PAGE_SIZE;
> +	} else {

You can keep a single level (and remove the brackets)

	if (IS_ENABLED(CONFIG_PPC_BOOK3E))
		atom_size = SZ_1M;
	else if (radix_enabled())
		atom_size = PAGE_SIZE;
	else if (mmu_linear_psize == MMU_PAGE_4K)
		atom_size = PAGE_SIZE;
	else
		atom_size = SZ_1M;


> +		/*
> +		 * Linear mapping is one of 4K, 1M and 16M.  For 4K, no need
> +		 * to group units.  For larger mappings, use 1M atom which
> +		 * should be large enough to contain a number of units.
> +		 */
> +		if (mmu_linear_psize == MMU_PAGE_4K)
> +			atom_size = PAGE_SIZE;
> +		else
> +			atom_size = 1 << 20;

Use SZ_1M instead of hardcoding.

> +	}
>   
>   	if (pcpu_chosen_fc != PCPU_FC_PAGE) {
>   		rc = pcpu_embed_first_chunk(0, dyn_size, atom_size, pcpu_cpu_distance,
>