kernel_optimize_test/Documentation/arm
Ard Biesheuvel 1eb7756902 ARM: 9012/1: move device tree mapping out of linear region
commit 7a1be318f5795cb66fa0dc86b3ace427fe68057f upstream

On ARM, setting up the linear region is tricky, given the constraints
around placement and alignment of the memblocks, and how the kernel
itself as well as the DT are placed in physical memory.

Let's simplify matters a bit, by moving the device tree mapping to the
top of the address space, right between the end of the vmalloc region
and the start of the the fixmap region, and create a read-only mapping
for it that is independent of the size of the linear region, and how it
is organized.

Since this region was formerly used as a guard region, which will now be
populated fully on LPAE builds by this read-only mapping (which will
still be able to function as a guard region for stray writes), bump the
start of the [underutilized] fixmap region by 512 KB as well, to ensure
that there is always a proper guard region here. Doing so still leaves
ample room for the fixmap space, even with NR_CPUS set to its maximum
value of 32.

Tested-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-05-19 10:13:18 +02:00
..
keystone
nwfpe
omap
pxa
sa1100
samsung
samsung-s3c24xx
spear
sti
stm32
sunxi
vfp
arm.rst
booting.rst
cluster-pm-race-avoidance.rst
firmware.rst
index.rst
interrupts.rst
ixp4xx.rst
kernel_mode_neon.rst
kernel_user_helpers.rst
marvel.rst
mem_alignment.rst
memory.rst ARM: 9012/1: move device tree mapping out of linear region 2021-05-19 10:13:18 +02:00
microchip.rst
netwinder.rst
porting.rst
setup.rst
sunxi.rst documentation: arm: sunxi: add Allwinner H6 documents 2020-10-28 11:19:24 -06:00
swp_emulation.rst
tcm.rst
uefi.rst efi: efivars: limit availability to X86 builds 2020-09-29 19:40:57 +02:00
vlocks.rst