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MIPS64: Support of at least 48 bits of SEGBITS

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SEGBITS is 40 bits or more, depending on CPU type.  Introduces optional
support for 48 bits of application virtual address space.  Only 16K and
64K pages are supported.

Enabling will result in a memory overhead of a small number of pages for
small applications.  For 64K pages a 3rd level of page tables is required
which has some impact during software TLB refill.

[ralf@linux-mips.org: Fixed things raised in the review of the version
posted and changed kconfig to be a bit more userfriendly.]

Signed-off-by: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Cc: aleksey.makarov@auriga.com
Cc: james.hogan@imgtec.com
Cc: paul.burton@imgtec.com
Cc: david.daney@cavium.com
Cc: peterz@infradead.org
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Cc: davidlohr@hp.com
Cc: kirill@shutemov.name
Cc: akpm@linux-foundation.org
Cc: mingo@kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/10051/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Leonid Yegoshin
2015-05-14 18:34:43 -07:00
committed by Ralf Baechle
parent 7939469da2
commit 1e321fa917
3 changed files with 29 additions and 8 deletions
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13
arch/mips/Kconfig
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@@ -2076,6 +2076,16 @@ config KVM_GUEST_TIMER_FREQ
emulation when determining guest CPU Frequency. Instead, the guest's
timer frequency is specified directly.
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.
If unsure, say N.
choice
prompt "Kernel page size"
default PAGE_SIZE_4KB
@@ -2083,6 +2093,7 @@ 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
@@ -2092,6 +2103,7 @@ config PAGE_SIZE_4KB
config PAGE_SIZE_8KB
bool "8kB"
depends on CPU_R8000 || CPU_CAVIUM_OCTEON
depends on !MIPS_VA_BITS_48
help
Using 8kB page size will result in higher performance kernel at
the price of higher memory consumption. This option is available
@@ -2110,6 +2122,7 @@ config PAGE_SIZE_16KB
config PAGE_SIZE_32KB
bool "32kB"
depends on CPU_CAVIUM_OCTEON
depends on !MIPS_VA_BITS_48
help
Using 32kB page size will result in higher performance kernel at
the price of higher memory consumption. This option is available