linux-kernel - Re: How to get the supported page sizes of aarch64? (and possible other architectures)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <87tuefhhyt.fsf@linaro.org>
Date:   Fri, 07 Jan 2022 11:46:58 +0000
From:   Alex Bennée <alex.bennee@...aro.org>
To:     Qu Wenruo <quwenruo.btrfs@....com>
Cc:     qemu-arm@...gnu.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: How to get the supported page sizes of aarch64? (and possible
 other architectures)


Qu Wenruo <quwenruo.btrfs@....com> writes:

> Hi,
>
> Recently I'm trying to boot a kernel with 16K page size, but edk2
> firmware failed to load the kernel on my CM4, with unsupported message:
>
>  Failed to execute Archlinux ARM (\Image-custom): Unsupported
>
> While 4K and 64K page sized kernels are fine to boot.
>
> A quick search shows that Cortex A processors support 4K and 64K page
> size, and 16K page size is not a mandatory requirement.
>
> On the other hand, other aarch64 processors, like Apple M1 only supports
> 4K and 16K page size, no 64K page size support.
>
>
> Although ARM documents show ID_AA64MMFR0_EL1 would report such info, is
> there any user space tool or kernel messages to show an
> end-user-friendly output about what page sizes are support?

Not that I'm aware of but a chunk of the ID registers are exposed to
user space to read (although some bits are masked). I think the kernel
hides the translation granules support and I think only exposes the page
size the kernel has booted into.

I guess you could hack the kernel to dump the real ID register value in
dmesg or something like that?

>
> Thanks,
> Qu


-- 
Alex Bennée