powerpc/Kconfig: Update config option based on page size.
Currently on PPC64 changing kernel pagesize from 4K to 64K leaves
FORCE_MAX_ZONEORDER set to 13 - which produces a compile error.
The error occurs because of the following constraint (from
include/linux/mmzone.h) being violated:
MAX_ORDER -1 + PAGESHIFT <= SECTION_SIZE_BITS.
Expanding this out, we get:
FORCE_MAX_ZONEBITS <= 25 - PAGESHIFT,
which requires, for a 64K page, FORCE_MAX_ZONEBITS <= 9. Thus set max
value of FORCE_MAX_ZONEORDER for 64K pages to 9, and 4K pages to 13.
Also, check the minimum value:
In include/linux/huge_mm.h, we have the constraint HPAGE_PMD_ORDER <
MAX_ORDER which expands out to:
PTE_INDEX_SIZE < FORCE_MAX_ZONEORDER.
PTE_INDEX_SIZE is:
9 (4k hash or no hash 4K pgtable) or
8 (64K hash or no hash 64K pgtable).
Thus a min value of 8 for 64K pages and 9 for 4K pages is reasonable.
So, update the range of FORCE_MAX_ZONEORDER from 9-64 to 8-9 for 64K pages
and from 13-64 to 9-13 for 4K pages.
Signed-off-by: Rashmica Gupta <rashmicy@gmail.com>
Reviewed-by: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 7cd32c0..fbebde0 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -605,9 +605,9 @@
config FORCE_MAX_ZONEORDER
int "Maximum zone order"
- range 9 64 if PPC64 && PPC_64K_PAGES
+ range 8 9 if PPC64 && PPC_64K_PAGES
default "9" if PPC64 && PPC_64K_PAGES
- range 13 64 if PPC64 && !PPC_64K_PAGES
+ range 9 13 if PPC64 && !PPC_64K_PAGES
default "13" if PPC64 && !PPC_64K_PAGES
range 9 64 if PPC32 && PPC_16K_PAGES
default "9" if PPC32 && PPC_16K_PAGES