Christophe Leroy <christophe.le...@csgroup.eu> writes:
> Le 13/10/2021 à 23:34, Joel Stanley a écrit :
>> The page_alloc.c code will call into __kernel_map_pages when
>> DEBUG_PAGEALLOC is configured and enabled.
>>
>> As the implementation assumes hash, this should crash spectacularly if
>> not for a bit of luck in __kernel_map_pages. In this function
>> linear_map_hash_count is always zero, the for loop exits without doing
>> any damage.
>>
>> There are no other platforms that determine if they support
>> debug_pagealloc at runtime. Instead of adding code to mm/page_alloc.c to
>> do that, this change turns the map/unmap into a noop when in radix
>> mode and prints a warning once.
>>
>> Signed-off-by: Joel Stanley <j...@jms.id.au>
>> ---
>> v2: Put __kernel_map_pages in pgtable.h
>>
>> arch/powerpc/include/asm/book3s/64/hash.h | 2 ++
>> arch/powerpc/include/asm/book3s/64/pgtable.h | 11 +++++++++++
>> arch/powerpc/include/asm/book3s/64/radix.h | 3 +++
>> arch/powerpc/mm/book3s64/hash_utils.c | 2 +-
>> arch/powerpc/mm/book3s64/radix_pgtable.c | 7 +++++++
>> 5 files changed, 24 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/powerpc/include/asm/book3s/64/hash.h
>> b/arch/powerpc/include/asm/book3s/64/hash.h
>> index d959b0195ad9..674fe0e890dc 100644
>> --- a/arch/powerpc/include/asm/book3s/64/hash.h
>> +++ b/arch/powerpc/include/asm/book3s/64/hash.h
>> @@ -255,6 +255,8 @@ int hash__create_section_mapping(unsigned long start,
>> unsigned long end,
>> int nid, pgprot_t prot);
>> int hash__remove_section_mapping(unsigned long start, unsigned long end);
>>
>> +void hash__kernel_map_pages(struct page *page, int numpages, int enable);
>> +
>> #endif /* !__ASSEMBLY__ */
>> #endif /* __KERNEL__ */
>> #endif /* _ASM_POWERPC_BOOK3S_64_HASH_H */
>> diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h
>> b/arch/powerpc/include/asm/book3s/64/pgtable.h
>> index 5d34a8646f08..265661ded238 100644
>> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
>> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
>> @@ -1101,6 +1101,17 @@ static inline void vmemmap_remove_mapping(unsigned
>> long start,
>> }
>> #endif
>>
>> +#ifdef CONFIG_DEBUG_PAGEALLOC
>> +static inline void __kernel_map_pages(struct page *page, int numpages, int
>> enable)
>> +{
>> + if (radix_enabled()) {
>> + radix__kernel_map_pages(page, numpages, enable);
>> + return;
>> + }
>> + hash__kernel_map_pages(page, numpages, enable);
>
> I'd have prefered something like below
>
> if (radix_enabled())
> radix__kernel_map_pages(page, numpages, enable);
> else
> hash__kernel_map_pages(page, numpages, enable);
I did that when applying.
cheers
