Re: [PATCH v3 06/52] xen/arm: introduce CONFIG_HAS_MMU

[Julien Grall <julien@xxxxxxx>]

Hi,

On 04/07/2023 12:14, Ayan Kumar Halder wrote:
> On 26/06/2023 04:33, Penny Zheng 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.
> >
> > This commit wants to introduce a new Kconfig CONFIG_HAS_MMU to guard
> > MMU-related codes, to tell two different memory management architecture:
> > VMAS and PMSA.
> >
> > In a VMSA system, a Memory Management Unit (MMU) provides fine-grained
> > control of a memory system through a set of virtual to physical address
> > mappings and associated memory properties held in memory-mapped tables
> > known as translation tables.
> >
> > Signed-off-by: Penny Zheng <penny.zheng@xxxxxxx>
> > Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
> > ---
> > v3:
> > - new patch
> > ---
> >   xen/arch/arm/Kconfig | 8 ++++++++
> >   1 file changed, 8 insertions(+)
> >
> > diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
> > index ff17345cdb..fb77392b82 100644
> > --- a/xen/arch/arm/Kconfig
> > +++ b/xen/arch/arm/Kconfig
> > @@ -60,6 +60,14 @@ config PADDR_BITS
> >
> >   source "arch/Kconfig"
> >
> > +config HAS_MMU
> > +       bool "Memory Management Unit support in a VMSA system"
> > +       default y
I don't think you can disable HAS_MMU right now. So you want to drop the 
description to prevent a user to select it. This could then be combined to
"def_bool y".

> > +       help
> > +         In a VMSA system, a Memory Management Unit (MMU) provides 
> > fine-grained control of
> > +         a memory system through a set of virtual to physical address 
> > mappings and associated memory
> > +         properties held in memory-mapped tables known as translation 
> > tables.
> > +
> >   config ACPI
> >          bool "ACPI (Advanced Configuration and Power Interface) 
> > Support (UNSUPPORTED)" if UNSUPPORTED
> >          depends on ARM_64
> I don't think you need this option.
I think we want to introduce a 'choice' where the user can select either 
the MPU or MMU. But not both.
This would be similar to how we select the Physical address space size.

Cheers,

--
Julien Grall