Re: [PATCH v2 16/40] xen/arm: introduce setup_mm_mappings

[Julien Grall <julien@xxxxxxx>]

Hi,

On 13/01/2023 05:28, Penny Zheng wrote:
> Function setup_pagetables is responsible for boot-time pagetable setup
> in MMU system.
> But in MPU system, we have already built up start-of-day Xen MPU memory region
> mapping at the very beginning in assembly.
>
> So in order to keep only one codeflow in arm/setup.c, setup_mm_mappings
> , with a more generic name, is introduced and act as an empty stub in
> MPU system.
is the empty stub temporarily?

> Signed-off-by: Penny Zheng <penny.zheng@xxxxxxx>
> Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
> ---
>   xen/arch/arm/include/asm/mm.h     |  2 ++
>   xen/arch/arm/include/asm/mm_mpu.h | 16 ++++++++++++++++
>   xen/arch/arm/setup.c              |  2 +-
>   3 files changed, 19 insertions(+), 1 deletion(-)
>   create mode 100644 xen/arch/arm/include/asm/mm_mpu.h
>
> diff --git a/xen/arch/arm/include/asm/mm.h b/xen/arch/arm/include/asm/mm.h
> index 1b9fdb6ff5..9b4c07d965 100644
> --- a/xen/arch/arm/include/asm/mm.h
> +++ b/xen/arch/arm/include/asm/mm.h
> @@ -243,6 +243,8 @@ static inline void __iomem *ioremap_wc(paddr_t start, 
> size_t len)
>   
>   #ifndef CONFIG_HAS_MPU
>   #include <asm/mm_mmu.h>
> +#else
> +#include <asm/mm_mpu.h>
>   #endif
>   
>   /* Page-align address and convert to frame number format */
> diff --git a/xen/arch/arm/include/asm/mm_mpu.h 
> b/xen/arch/arm/include/asm/mm_mpu.h
> new file mode 100644
> index 0000000000..1f3cff7743
> --- /dev/null
> +++ b/xen/arch/arm/include/asm/mm_mpu.h
> @@ -0,0 +1,16 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +#ifndef __ARCH_ARM_MM_MPU__
> +#define __ARCH_ARM_MM_MPU__
> +
> +#define setup_mm_mappings(boot_phys_offset) ((void)(boot_phys_offset))
> +
> +#endif /* __ARCH_ARM_MM_MPU__ */
> +
> +/*
> + * Local variables:
> + * mode: C
> + * c-file-style: "BSD"
> + * c-basic-offset: 4
> + * indent-tabs-mode: nil
> + * End:
> + */
> diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
> index 1f26f67b90..d7d200179c 100644
> --- a/xen/arch/arm/setup.c
> +++ b/xen/arch/arm/setup.c
> @@ -1003,7 +1003,7 @@ void __init start_xen(unsigned long boot_phys_offset,
>       /* Initialize traps early allow us to get backtrace when an error 
> occurred */
>       init_traps();
>   
> -    setup_pagetables(boot_phys_offset);
> +    setup_mm_mappings(boot_phys_offset);
You are renaming the caller but not the function. Why?

>   
>       smp_clear_cpu_maps();
>   
Cheers,

--
Julien Grall