On 18/09/2025 22:10, Will Deacon wrote:

On Wed, 17 Sep 2025 12:02:06 -0700, Yang Shi wrote:

quoted

On systems with BBML2_NOABORT support, it causes the linear map to be mapped
with large blocks, even when rodata=full, and leads to some nice performance
improvements.

Ryan tested v7 on an AmpereOne system (a VM with 12G RAM) in all 3 possible
modes by hacking the BBML2 feature detection code:

[...]

Applied patches 1 and 3 to arm64 (for-next/mm), thanks!

[1/5] arm64: Enable permission change on arm64 kernel block mappings
      https://git.kernel.org/arm64/c/a660194dd101
[3/5] arm64: mm: support large block mapping when rodata=full
      https://git.kernel.org/arm64/c/a166563e7ec3

I also picked up the BBML allow-list addition (second patch) on
for-next/cpufeature.

The fourth patch ("arm64: mm: split linear mapping if BBML2 unsupported
on secondary CPUs") has some really horrible conflicts. These are partly
due to some of the type cleanups on for-next/mm but I think mainly due
to Kevin's kpti rework that landed after -rc1.

Thanks Will, although I'm nervous that without this patch, some platforms might
not boot; Wikipedia tells me that there are some Google, Mediatek and Qualcomm
SoCs that pair X4 CPUs (which is on the BBML2_NOABORT allow list) with A720
and/or A520 (which are not). See previous mail at [1].

I'd be happy to rebase it if you can let me know the prefered base SHA/tree?

[1]
https://lore.kernel.org/linux-arm-kernel/11f84d00-8c76-402d-bbad-014a3542992f@arm.com/ (local)

Thanks,
Ryan

So I think the best bet might be to leave that one for next time, if
that's ok?

Cheers,