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authorAlex Belits <alex.belits@cavium.com>2017-02-16 17:27:34 -0800
committerRalf Baechle <ralf@linux-mips.org>2017-04-10 11:56:06 +0200
commit3377e227af441aff710726437adc20efc359fd9c (patch)
treed05610ba07eca74f783b42fbbd5110b7876d8c9b /arch/mips/Kconfig
parentdfa32261fa0ed1821c7d5dbb9e93eddfe311a0d9 (diff)
downloadlinux-3377e227af441aff710726437adc20efc359fd9c.tar.bz2
MIPS: Add 48-bit VA space (and 4-level page tables) for 4K pages.
Some users must have 4K pages while needing a 48-bit VA space size. The cleanest way do do this is to go to a 4-level page table for this case. Each page table level using order-0 pages adds 9 bits to the VA size (at 4K pages, so for four levels we get 9 * 4 + 12 == 48-bits. For the 4K page size case only we add support functions for the PUD level of the page table tree, also the TLB exception handlers get an extra level of tree walk. [david.daney@cavium.com: Forward port to v4.10.] [david.daney@cavium.com: Forward port to v4.11.] Signed-off-by: Alex Belits <alex.belits@cavium.com> Signed-off-by: David Daney <david.daney@cavium.com> Cc: James Hogan <james.hogan@imgtec.com> Cc: Alex Belits <alex.belits@cavium.com> Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/15312/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Diffstat (limited to 'arch/mips/Kconfig')
-rw-r--r--arch/mips/Kconfig13
1 files changed, 8 insertions, 5 deletions
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 68af16b72e9c..f4dd2c322d4b 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -2121,10 +2121,13 @@ config MIPS_VA_BITS_48
bool "48 bits virtual memory"
depends on 64BIT
help
- Support a maximum at least 48 bits of application virtual memory.
- Default is 40 bits or less, depending on the CPU.
- This option result in a small memory overhead for page tables.
- This option is only supported with 16k and 64k page sizes.
+ Support a maximum at least 48 bits of application virtual
+ memory. Default is 40 bits or less, depending on the CPU.
+ For page sizes 16k and above, this option results in a small
+ memory overhead for page tables. For 4k page size, a fourth
+ level of page tables is added which imposes both a memory
+ overhead as well as slower TLB fault handling.
+
If unsure, say N.
choice
@@ -2134,7 +2137,6 @@ choice
config PAGE_SIZE_4KB
bool "4kB"
depends on !CPU_LOONGSON2 && !CPU_LOONGSON3
- depends on !MIPS_VA_BITS_48
help
This option select the standard 4kB Linux page size. On some
R3000-family processors this is the only available page size. Using
@@ -2983,6 +2985,7 @@ config HAVE_LATENCYTOP_SUPPORT
config PGTABLE_LEVELS
int
+ default 4 if PAGE_SIZE_4KB && MIPS_VA_BITS_48
default 3 if 64BIT && !PAGE_SIZE_64KB
default 2