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

[Ayan Kumar Halder <ayankuma@xxxxxxx>]

On 04/07/2023 12:44, Julien Grall wrote:
> 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.
+1 (I like this approach).

> This would be similar to how we select the Physical address space size.
>
> Cheers,