Balbir Singh <bsinghar...@gmail.com> writes:
> On 20/09/16 03:31, Aneesh Kumar K.V wrote:
>> For hugetlb to work with 4K page size, we need the MAX_ORDER to be more
>> than 13. When switching from a 64K page size to 4K linux page size using
>> make nconfig, we endup with a CONFIG_FORCE_MAX_ZONEORDER value of 9.
>> This results in 16M hugepage to be considered as a gigantic huge page
>> which inturn can result in failure to setup hugepages if gigantic
>> hugepage support is not enabled.
>>
>> This also results in kernel crash with 4K radix configuration. We
>> hit the below BUG_ON on radix
>>
>> kernel BUG at mm/huge_memory.c:364!
>> Oops: Exception in kernel mode, sig: 5 [#1]
>> SMP NR_CPUS=2048 NUMA PowerNV
>> Modules linked in:
>> CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.8.0-rc1-00006-gbae9cc6 #1
>> task: c0000000f1af8000 task.stack: c0000000f1aec000
>> NIP: c000000000c5fa0c LR: c000000000c5f9d8 CTR: c000000000c5f9a4
>> REGS: c0000000f1aef920 TRAP: 0700 Not tainted (4.8.0-rc1-00006-gbae9cc6)
>> MSR: 9000000102029033 <SF,HV,VEC,EE,ME,IR,DR,RI,LE,TM[E]> CR: 24000844
>> XER: 00000000
>> CFAR: c000000000c5f9e0 SOFTE: 1
>> .....
>> NIP [c000000000c5fa0c] hugepage_init+0x68/0x238
>> LR [c000000000c5f9d8] hugepage_init+0x34/0x238
>>
>> Fixes: a7ee539584acf ("powerpc/Kconfig: Update config option based on page
>> size")
>>
>> Reported-by: Santhosh <santh...@linux.vnet.ibm.com>
>> Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.vnet.ibm.com>
>> ---
>> arch/powerpc/Kconfig | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
>> index 927d2ab2ce08..792cb1768c8f 100644
>> --- a/arch/powerpc/Kconfig
>> +++ b/arch/powerpc/Kconfig
>> @@ -637,7 +637,7 @@ config FORCE_MAX_ZONEORDER
>> int "Maximum zone order"
>> range 8 9 if PPC64 && PPC_64K_PAGES
>> default "9" if PPC64 && PPC_64K_PAGES
>> - range 9 13 if PPC64 && !PPC_64K_PAGES
>> + range 13 13 if PPC64 && !PPC_64K_PAGES
>
> Do we need the range to be 12 13?
static inline bool hstate_is_gigantic(struct hstate *h)
{
return huge_page_order(h) >= MAX_ORDER;
}
We consider hstate gigantic if it also == MAX_ORDER. Hence it should
be > 12 .
>
>> default "13" if PPC64 && !PPC_64K_PAGES
>> range 9 64 if PPC32 && PPC_16K_PAGES
>> default "9" if PPC32 && PPC_16K_PAGES
>>
>
> Otherwise
>
> Acked-by: Balbir Singh <bsinghar...@gmail.com>
