Re: [PATCH] Documentation/arm64: add memory layout with 4KB pages + VA39-bit
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From: Catalin Marinas <catalin.marinas@arm.com>
Date: 2021-10-06 17:14:45
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linux-arm-kernel, lkml
On Thu, Sep 30, 2021 at 06:50:26PM +0800, Jisheng Zhang wrote:
quoted hunk ↗ jump to hunk
The 4KB pages + 3 levels (39-bit) combination is also widely used in arm64 world, add the memory layout description for this combination. Signed-off-by: Jisheng Zhang <redacted> --- Documentation/arm64/memory.rst | 17 +++++++++++++++++ 1 file changed, 17 insertions(+)diff --git a/Documentation/arm64/memory.rst b/Documentation/arm64/memory.rst index 901cd094f4ec..d1745b570f0c 100644 --- a/Documentation/arm64/memory.rst +++ b/Documentation/arm64/memory.rst@@ -26,6 +26,23 @@ The swapper_pg_dir address is written to TTBR1 and never written to TTBR0. +AArch64 Linux memory layout with 4KB pages + 3 levels (39-bit):: + Start End Size Use + ----------------------------------------------------------------------- + 0000000000000000 0000007fffffffff 512GB user + ffffff8000000000 ffffffbfffffffff 256GB kernel logical memory map + [ffffffb000000000 ffffffbfffffffff] 64GB [kasan shadow region] + ffffffc000000000 ffffffc007ffffff 128MB bpf jit region + ffffffc008000000 ffffffc00fffffff 128MB modules + ffffffc010000000 fffffffdefffffff 253440MB vmalloc + fffffffdf0000000 fffffffdfdffffff 224MB fixed mappings (top down) + fffffffdfe000000 fffffffdfe7fffff 8MB [guard region] + fffffffdfe800000 fffffffdff7fffff 16MB PCI I/O space + fffffffdff800000 fffffffdffffffff 8MB [guard region] + fffffffe00000000 ffffffffefffffff 4GB vmemmap + ffffffff00000000 ffffffffffffffff 4GB [guard region]
I wouldn't bother maintaining these. There are other combinations that
people may use. The 4KB + 48-bit VA is defconfig while 64KB + 52-bit was
more interesting, so we thought it would be useful.
I'm more inclined to remove them altogether and maybe just add some
high-level ascii art as per the log of commit f4693c2716b3 ("arm64: mm:
extend linear region for 52-bit VA configurations").
--
Catalin