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?
> 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>
