Re: [PATCH v2 7/7] arm/mpu: Implement setup_mpu for MPU system

[Ayan Kumar Halder <ayankuma@xxxxxxx>]

On 08/04/2025 14:51, Luca Fancellu wrote:
> Hi Ayan,
Hi Luca,
> > On 8 Apr 2025, at 14:32, Ayan Kumar Halder <ayankuma@xxxxxxx> wrote:
> >
> > Hi Luca,
> >
> > On 07/04/2025 10:14, Luca Fancellu wrote:
> > > CAUTION: This message has originated from an External Source. Please use proper 
> > > judgment and caution when opening attachments, clicking links, or responding to 
> > > this email.
> > >
> > >
> > > Implement the function setup_mpu that will logically track the MPU
> > > regions defined by hardware registers, start introducing data
> > > structures and functions to track the status from the C world.
> > >
> > > The xen_mpumap_mask bitmap is used to track which MPU region are
> > > enabled at runtime.
> > >
> > > This function is called from setup_mm() which full implementation
> > > will be provided in a later stage.
> > >
> > > Signed-off-by: Luca Fancellu <luca.fancellu@xxxxxxx>
> > > ---
> > >   xen/arch/arm/include/asm/arm64/mpu.h |  2 ++
> > >   xen/arch/arm/mpu/mm.c                | 49 +++++++++++++++++++++++++++-
> > >   2 files changed, 50 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/xen/arch/arm/include/asm/arm64/mpu.h 
> > > b/xen/arch/arm/include/asm/arm64/mpu.h
> > > index 7cf8d355a1af..ff5a957bf085 100644
> > > --- a/xen/arch/arm/include/asm/arm64/mpu.h
> > > +++ b/xen/arch/arm/include/asm/arm64/mpu.h
> > > @@ -6,6 +6,8 @@
> > >   #ifndef __ARM_ARM64_MPU_H__
> > >   #define __ARM_ARM64_MPU_H__
> > >
> > > +#define PRENR_MASK  GENMASK(31, 0)
> > This can be moved to xen/arch/arm/include/asm/mpu.h
> I can see from the Arm® Cortex®-R52 Processor TRM, r1p1, 3.3.46 Hyp MPU Region 
> Enable Register,
> that HPRENR can have 16/20/24 enabled bits, the rest is RAZ.
Yes, I see that. However, if you see ARM DDI 0568A.c ID110520 ArmV8-R32 
supplement
E2.2.4 HPRENR

Provides direct access to the HPRLAR.EN bits for EL2 MPU regions 0 to 31.

AFAIU, the maximum number of EL2 MPU regions will always be 32. This 
doesnot seem to be configurable.
The R52 TRM isn't clear when it says "{no,16,20,24} EL2-controlled MPU 
regions implemented" as there is no register to set/check how many EL2 
MPU regions are implemented.
So, I suggest we can keep this in the common file for now.

- Ayan

> Because of that I’ve put that here, maybe you should implement it in the arm32 
> part since you have this
> difference from Arm64.
>
> Cheers,
> Luca