Re: [PATCH 3/4] ARM: drop CONFIG_HIGHPTE support

Sebastian Andrzej Siewior
2024-12-11T14:25:21Z

On 2024-12-10 17:05:55 [+0100], Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
>
> CONFIG_HIGHPTE was added in linux-2.6.32, a few years before 64-bit
> support. At the time it made sense, as the CONFIG_ARM_LPAE option allowed
> systems with 16GB of memory that made lowmem a particularly scarce
> resource, and the HIGHPTE implementation gave feature parity with 32-bit
> x86 and frv machines.
>
> Since Arm is the last architecture remaining that uses this, and almost
> no 32-bit machines support more than 4GB of RAM, the cost of continuing
> to maintain HIGHPTE seems unjustified, so remove it here to allow
> simplifying the generic page table handling.
>
> Link: https://lore.kernel.org/lkml/20241204103042.1904639-8-arnd@kernel.org/T/#u
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> I sent a patch to drop HIGHPTE support on x86 today, see
> https://lore.kernel.org/lkml/20241210144945.2325330-9-arnd@kernel.org/T/#u
>
> If that one gets merged, we can merge this one instead of the one
> that makes HIGHPTE depend on !PREEMPT_RT, but if we decide against
> the x86 change, then we probably don't want this one either.

Based on what I have written in 20241211140402.yf7gMExr@linutronix.de it
makes sense.

Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Sebastian