Re: [PATCH v3 52/52] xen/arm: add Kconfig option CONFIG_HAS_MPU to enable MPU system support

[Ayan Kumar Halder <ayankuma@xxxxxxx>]

On 26/06/2023 04:34, Penny Zheng wrote:
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>
> Introduce a Kconfig option CONFIG_HAS_MPU to enable MPU architecture
> support. STATIC_MEMORY, ARCH_MAP_DOMAIN_PAGE and ARM_SECURE_STATE will
> be selected by MPU system by default. Also, features like, ARM_EFI, are
> not supported right now.
>
> Current MPU system design is only for ARM 64-bit platform.
>
> Signed-off-by: Penny Zheng <penny.zheng@xxxxxxx>
> Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
> ---
> v3:
> - select ARCH_MAP_DOMAIN_PAGE and ARM_SECURE_STATE
> - remove platform-specific config: CONFIG_ARM_V8R
> ---
>   xen/arch/arm/Kconfig | 14 +++++++++++++-
>   1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
> index 3f67aacbbf..2acdf39ec8 100644
> --- a/xen/arch/arm/Kconfig
> +++ b/xen/arch/arm/Kconfig
> @@ -62,6 +62,7 @@ source "arch/Kconfig"
>   config HAS_MMU
>          bool "Memory Management Unit support in a VMSA system"
>          default y
> +       depends on !HAS_MPU
>          select HAS_PAGING_MEMPOOL
>          select HAS_PMAP
>          select HAS_VMAP
> @@ -70,6 +71,17 @@ config HAS_MMU
>            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 HAS_MPU
> +       bool "Memory Protection Unit support in a PMSA system"
> +       default n
> +       depends on ARM_64
This will not be true as R52 will support MPU
> +       select ARCH_MAP_DOMAIN_PAGE
> +       select ARM_SECURE_STATE
Also, R52 does not support secure state.
> +       select STATIC_MEMORY
> +       help
> +         The PMSA is based on a Memory Protection Unit (MPU), which provides a 
> much simpler
> +         memory protection scheme than the MMU based VMSA.
> +
Instead, I will suggest something like this :-

config ARM_V8R
    bool "ARMv8-R AArch64 architecture support (UNSUPPORTED)" if 
UNSUPPORTED
    default n
    select HAS_MPU
    select ARM_SECURE_STATE
    select STATIC_MEMORY
    depends on ARM_64
    help
      This option enables Armv8-R profile for Arm64. Enabling this option
      results in selecting MPU.


So, that later on we can add :-

config AARCH32_V8R
    bool "AArch32 Arm V8R Support (UNSUPPORTED)" if UNSUPPORTED
    default n
    select HAS_MPU
    select STATIC_MEMORY
    depends on ARM_32
    help
      This option enables Armv8-R profile for Arm32.

- Ayan

>   config HAS_FIXMAP
>          bool "Provide special-purpose 4K mapping slots in a VMSA"
>          depends on HAS_MMU
> @@ -85,7 +97,7 @@ config ACPI
>
>   config ARM_EFI
>          bool "UEFI boot service support"
> -       depends on ARM_64
> +       depends on ARM_64 && !HAS_MPU
>          default y
>          help
>            This option provides support for boot services through
> --
> 2.25.1