Subject: Re: [RFC PATCH 1/5] powerpc/64s: update_mmu_cache inline the radix test

From: Nicholas Piggin <[email-masked]>
Date: Tue, 22 Dec 2020 13:32:20 +1000

Excerpts from Christophe Leroy's message of December 20, 2020 9:37 pm:
> 
> 
> Le 20/12/2020 à 00:48, Nicholas Piggin a écrit :
>> This allows the function to be entirely noped if hash support is
>> compiled out (not possible yet).
>> 
>> Signed-off-by: Nicholas Piggin <[email-masked]>
>> ---
>>   arch/powerpc/include/asm/book3s/pgtable.h | 11 ++++++++++-
>>   arch/powerpc/mm/book3s32/mmu.c            |  4 ++--
>>   arch/powerpc/mm/book3s64/hash_utils.c     |  7 ++-----
>>   3 files changed, 14 insertions(+), 8 deletions(-)
>> 
>> diff --git a/arch/powerpc/include/asm/book3s/pgtable.h b/arch/powerpc/include/asm/book3s/pgtable.h
>> index 0e1263455d73..914e9fc7b069 100644
>> --- a/arch/powerpc/include/asm/book3s/pgtable.h
>> +++ b/arch/powerpc/include/asm/book3s/pgtable.h
>> @@ -35,7 +35,16 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
>>    * corresponding HPTE into the hash table ahead of time, instead of
>>    * waiting for the inevitable extra hash-table miss exception.
>>    */
>> -void update_mmu_cache(struct vm_area_struct *vma, unsigned long address, pte_t *ptep);
>> +void hash__update_mmu_cache(struct vm_area_struct *vma, unsigned long address, pte_t *ptep);
>> +
>> +static inline void update_mmu_cache(struct vm_area_struct *vma, unsigned long address, pte_t *ptep)
>> +{
>> +#ifdef CONFIG_PPC64
> 
> You shouldn't need that ifdef. radix_enabled() is always defined.

True, thanks.

>> +	if (radix_enabled())
>> +		return;
>> +#endif
>> +	hash__update_mmu_cache(vma, address, ptep);
>> +}
>>   
>>   #endif /* __ASSEMBLY__ */
>>   #endif
>> diff --git a/arch/powerpc/mm/book3s32/mmu.c b/arch/powerpc/mm/book3s32/mmu.c
>> index 859e5bd603ac..c5a570ca37ff 100644
>> --- a/arch/powerpc/mm/book3s32/mmu.c
>> +++ b/arch/powerpc/mm/book3s32/mmu.c
>> @@ -325,8 +325,8 @@ static void hash_preload(struct mm_struct *mm, unsigned long ea)
>>    *
>>    * This must always be called with the pte lock held.
>>    */
>> -void update_mmu_cache(struct vm_area_struct *vma, unsigned long address,
>> -		      pte_t *ptep)
>> +void hash__update_mmu_cache(struct vm_area_struct *vma, unsigned long address,
>> +			    pte_t *ptep)
> 
> Now the limit is 100 chars per line. This should fit on a single line I think.

I never quite know what to do here. The Linux limit is 100 but 80 is 
still preferred AFAIK (e.g., don't make lots of lines beyond 80), but 
80-100 can be used in some cases when splitting the line doesn't improve 
readability on 80 colums.

This does (slightly) improve readability.

Thanks,
Nick

> 
>>   {
>>   	if (!mmu_has_feature(MMU_FTR_HPTE_TABLE))
>>   		return;
>> diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c
>> index 73b06adb6eeb..d52a3dee7cf2 100644
>> --- a/arch/powerpc/mm/book3s64/hash_utils.c
>> +++ b/arch/powerpc/mm/book3s64/hash_utils.c
>> @@ -1667,8 +1667,8 @@ static void hash_preload(struct mm_struct *mm, pte_t *ptep, unsigned long ea,
>>    *
>>    * This must always be called with the pte lock held.
>>    */
>> -void update_mmu_cache(struct vm_area_struct *vma, unsigned long address,
>> -		      pte_t *ptep)
>> +void hash__update_mmu_cache(struct vm_area_struct *vma, unsigned long address,
>> +			    pte_t *ptep)
> 
> Now the limit is 100 chars per line. This should fit on a single line I think.
> 
>>   {
>>   	/*
>>   	 * We don't need to worry about _PAGE_PRESENT here because we are
>> @@ -1677,9 +1677,6 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned long address,
>>   	unsigned long trap;
>>   	bool is_exec;
>>   
>> -	if (radix_enabled())
>> -		return;
>> -
>>   	/* We only want HPTEs for linux PTEs that have _PAGE_ACCESSED set */
>>   	if (!pte_young(*ptep) || address >= TASK_SIZE)
>>   		return;
>> 
>