On Thu, Sep 30, 2021 at 06:50:26PM +0800, Jisheng Zhang wrote:
> 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 <Jisheng.Zhang@xxxxxxxxxxxxx>
> ---
> 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
