Excerpts from Christophe Leroy's message of October 21, 2021 2:52 pm:
>
>
> 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 <npig...@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;
I could but the below comment and logic applies to BookS hash so I'm
happier to put it in its own block. Radix later might also inherit a
comment and size from x86-64.
>> + /*
>> + * 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.
Sure.
Thanks,
Nick
