Re: [Xen-devel] [PATCH v2 27/35] xen/arm32: head: Document create_pages_tables()

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 22 Jul 2019, Julien Grall wrote:
> Document the behavior and the main registers usage within the function.
> Note that r6 is now only used within the function, so it does not need
> to be part of the common register.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxx>

Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> ---
>     Changes in v2:
>         - Patch added
> ---
>  xen/arch/arm/arm32/head.S | 30 +++++++++++++++++++-----------
>  1 file changed, 19 insertions(+), 11 deletions(-)
> 
> diff --git a/xen/arch/arm/arm32/head.S b/xen/arch/arm/arm32/head.S
> index 119d2a0df8..ef8979959b 100644
> --- a/xen/arch/arm/arm32/head.S
> +++ b/xen/arch/arm/arm32/head.S
> @@ -53,7 +53,7 @@
>   *   r3  -
>   *   r4  -
>   *   r5  -
> - *   r6  - identity map in place
> + *   r6  -
>   *   r7  -
>   *   r8  - DTB address (boot CPU only)
>   *   r9  - paddr(start)
> @@ -301,18 +301,26 @@ cpu_init_done:
>          mov   pc, r5                        /* Return address is in r5 */
>  ENDPROC(cpu_init)
>  
> +/*
> + * Rebuild the boot pagetable's first-level entries. The structure
> + * is described in mm.c.
> + *
> + * After the CPU enables paging it will add the fixmap mapping
> + * to these page tables, however this may clash with the 1:1
> + * mapping. So each CPU must rebuild the page tables here with
> + * the 1:1 in place.
> + *
> + * Inputs:
> + *   r9 : paddr(start)
> + *   r10: phys offset
> + *
> + * Clobbers r0 - r6
> + *
> + * Register usage within this function:
> + *   r6 : Identity map in place
> + */
>  create_page_tables:
>          /*
> -         * Rebuild the boot pagetable's first-level entries. The structure
> -         * is described in mm.c.
> -         *
> -         * After the CPU enables paging it will add the fixmap mapping
> -         * to these page tables, however this may clash with the 1:1
> -         * mapping. So each CPU must rebuild the page tables here with
> -         * the 1:1 in place.
> -         */
> -
> -        /*
>           * If Xen is loaded at exactly XEN_VIRT_START then we don't
>           * need an additional 1:1 mapping, the virtual mapping will
>           * suffice.
> -- 
> 2.11.0
> 

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