Re: [PATCH v1 1/4] xen/arm: mpu: Introduce choice between MMU and MPU

[Julien Grall <julien@xxxxxxx>]

Hi,

On 28/08/2024 15:44, Ayan Kumar Halder wrote:
> On 27/08/2024 11:37, Julien Grall wrote:
> > Hi,
> Hi Julien,
> > On 23/08/2024 17:31, Ayan Kumar Halder wrote:
> > > There are features in the forthcoming patches which are dependent on
> > > MPU. For eg fixed start address.
> > > Also, some of the Xen features (eg STATIC_MEMORY) will be selected
> > > by the MPU configuration.
> > >
> > > Thus, this patch introduces a choice between MMU and MPU for the type
> > > of memory management system. By default, MMU is selected.
> > > All the current platforms are now made dependent on MMU.
> > >
> > > Signed-off-by: Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>
> > > ---
> > >   xen/arch/arm/Kconfig           | 17 ++++++++++++++++-
> > >   xen/arch/arm/platforms/Kconfig |  2 +-
> > >   2 files changed, 17 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
> > > index 323c967361..686948cefd 100644
> > > --- a/xen/arch/arm/Kconfig
> > > +++ b/xen/arch/arm/Kconfig
> > > @@ -58,10 +58,25 @@ config PADDR_BITS
> > >       default 40 if ARM_PA_BITS_40
> > >       default 48 if ARM_64
> > >   +choice
> > > +    prompt "Memory management system"
> > > +    default MMU if ARM
> > > +    help
> > > +      User can choose between the different forms of memory 
> > > management system.
> > > +      Most of the Arm based systems support MMU.
> > I feel this is quite subjective. So I would drop it.
> Agreed.
> > > +
> > >   config MMU
> > > -    def_bool y
> > > +    bool "MMU"
> > >       select HAS_PMAP
> > >       select HAS_VMAP
> > > +    help
> > > +      Memory management unit is supported on most Arm based systems.
> > For this case, I would write "Select it you are plan to run Xen on 
> > Armv7-A or Armv8-A".
> Ack.
Actually, thinking a bit more. We should be able to run Xen on Armv9. So 
maybe it would be beter to write:
"Select it if you plan to run Xen on A-profile Armv7+".

Cheers,

--
Julien Grall