Re: [PATCH v3 1/4] xen: arm: Add a new helper update_boot_mapping()

[Michal Orzel <michal.orzel@amd.com>]

Hi Ayan,

On 13/08/2024 19:13, Ayan Kumar Halder wrote:
> update_boot_mapping() invokes update_identity_mapping() for the MMU specific
> code.
> Later when the MPU code is added, update_boot_mapping() would invoke the
> equivalent.
> 
> The common code now invokes update_boot_mapping() instead of
> update_identity_mapping(). So, that there is clear abstraction between the
> common and MMU/MPU specific logic.
> 
> This is in continuation to commit
> f661a20aa880: "Extract MMU-specific MM code".
> 
> update_identity_mapping() is now marked as static as it is called within
> xen/arch/arm/arm64/mmu/mm.c only. Also, updated the prototype to
> update_boot_mapping() which is now invoked from other files.
> 
> Signed-off-by: Ayan Kumar Halder <ayan.kumar.halder@amd.com>
> ---
> Changes from :-
> 
> v1 - 1. Introduced update_boot_mapping() which invokes
> update_identity_mapping() in MMU specific code.
> 
> v2 - 1. Make update_identity_mapping() static and update the prototype.
> 
>  xen/arch/arm/arm64/mmu/mm.c         | 7 ++++++-
>  xen/arch/arm/arm64/smpboot.c        | 6 +++---
>  xen/arch/arm/include/asm/arm64/mm.h | 2 +-
>  3 files changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/xen/arch/arm/arm64/mmu/mm.c b/xen/arch/arm/arm64/mmu/mm.c
> index 293acb67e0..1afbbeda5a 100644
> --- a/xen/arch/arm/arm64/mmu/mm.c
> +++ b/xen/arch/arm/arm64/mmu/mm.c
> @@ -111,7 +111,7 @@ void __init arch_setup_page_tables(void)
>      prepare_runtime_identity_mapping();
>  }
>  
> -void update_identity_mapping(bool enable)
> +static void update_identity_mapping(bool enable)
>  {
>      paddr_t id_addr = virt_to_maddr(_start);
>      int rc;
> @@ -125,6 +125,11 @@ void update_identity_mapping(bool enable)
>      BUG_ON(rc);
>  }
>  
> +void update_boot_mapping(bool enable)
> +{
> +    update_identity_mapping(enable);
> +}
> +
>  extern void switch_ttbr_id(uint64_t ttbr);
>  
>  typedef void (switch_ttbr_fn)(uint64_t ttbr);
> diff --git a/xen/arch/arm/arm64/smpboot.c b/xen/arch/arm/arm64/smpboot.c
> index a225fae64d..789f352ab6 100644
> --- a/xen/arch/arm/arm64/smpboot.c
> +++ b/xen/arch/arm/arm64/smpboot.c
> @@ -112,18 +112,18 @@ int arch_cpu_up(int cpu)
>      if ( !smp_enable_ops[cpu].prepare_cpu )
>          return -ENODEV;
>  
> -    update_identity_mapping(true);
> +    update_boot_mapping(true);
>  
>      rc = smp_enable_ops[cpu].prepare_cpu(cpu);
>      if ( rc )
> -        update_identity_mapping(false);
> +        update_boot_mapping(false);
>  
>      return rc;
>  }
>  
>  void arch_cpu_up_finish(void)
>  {
> -    update_identity_mapping(false);
> +    update_boot_mapping(false);
>  }
>  
>  /*
> diff --git a/xen/arch/arm/include/asm/arm64/mm.h b/xen/arch/arm/include/asm/arm64/mm.h
> index e0bd23a6ed..ac8d1f5c78 100644
> --- a/xen/arch/arm/include/asm/arm64/mm.h
> +++ b/xen/arch/arm/include/asm/arm64/mm.h
> @@ -21,7 +21,7 @@ void arch_setup_page_tables(void);
>   * Note that nested call (e.g. enable=true, enable=true) is not
>   * supported.
>   */
> -void update_identity_mapping(bool enable);
> +void update_boot_mapping(bool enable);
The whole point of adding a wrapper was to avoid ambiguity \wrt identity mapping and MPU.
You changed the name of a function but left the comment which is pretty MMU specific. I think
it should be moved to update_identity_mapping.

Apart from that:
Reviewed-by: Michal Orzel <michal.orzel@amd.com>

~Michal