[PATCH v1] arm64: head.S: Do not trap access to MPAMSM_EL1

[Fuad Tabba]

Hi Marc,

On Wed, 5 Feb 2025 at 17:02, Marc Zyngier <maz at kernel.org> wrote:
>
> On Wed, 05 Feb 2025 16:46:27 +0000,
> Fuad Tabba <tabba at google.com> wrote:
> >
> > Bit 50 of MPAM2_EL2, EnMPAMSM, traps access to MPAMSM_EL1 when 0,
> > as per ARM ARM DDI DDI0487L.a, section D24.12.3. Therefore,
> > ensure it is set to 1 for the host to disable the traps.
>
> But what makes use of this register in the kernel? I can't find any
> trace of it in 6.14-rc1.

I understand that MPAM support in the kernel isn't there quite yet.
Also, regarding enabling access to a register at EL1, without the
whole framework for enabling MPAM, might be problematic. It makes more
sense for this to be part of the work to add MPAM support, which I
believe James might be working on.

Cheers,
/fuad

> Thanks,
>
>         M.
>
> --
> Without deviation from the norm, progress is not possible.