Re: [PATCH v3 11/18] xen/arm: Enable use of dump_pt_walk() early during boot

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 12 Dec 2022, Julien Grall wrote:
> From: Julien Grall <jgrall@xxxxxxxxxx>
> 
> At the moment, dump_pt_walk() is using map_domain_page() to map
> the page tables.
> 
> map_domain_page() is only usuable after init_domheap_mappings() is called
> (arm32) or the xenheap has been initialized (arm64).
> 
> This means it can be hard to diagnose incorrect page-tables during
> early boot. So update dump_pt_walk() to xen_{, un}map_table() instead.
> 
> Note that the two helpers are moved earlier to avoid forward declaring
> them.
> 
> Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> ---
>  xen/arch/arm/mm.c | 56 +++++++++++++++++++++++------------------------
>  1 file changed, 28 insertions(+), 28 deletions(-)
> 
> diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
> index 1315a2c87db7..d0b1cf55f550 100644
> --- a/xen/arch/arm/mm.c
> +++ b/xen/arch/arm/mm.c
> @@ -191,6 +191,30 @@ static void __init __maybe_unused build_assertions(void)
>  #undef CHECK_DIFFERENT_SLOT
>  }
>  
> +static lpae_t *xen_map_table(mfn_t mfn)
> +{
> +    /*
> +     * During early boot, map_domain_page() may be unusable. Use the
> +     * PMAP to map temporarily a page-table.
> +     */
> +    if ( system_state == SYS_STATE_early_boot )
> +        return pmap_map(mfn);
> +
> +    return map_domain_page(mfn);
> +}
> +
> +static void xen_unmap_table(const lpae_t *table)
> +{
> +    /*
> +     * During early boot, xen_map_table() will not use map_domain_page()
> +     * but the PMAP.
> +     */
> +    if ( system_state == SYS_STATE_early_boot )
> +        pmap_unmap(table);
> +    else
> +        unmap_domain_page(table);
> +}
> +
>  void dump_pt_walk(paddr_t ttbr, paddr_t addr,
>                    unsigned int root_level,
>                    unsigned int nr_root_tables)
> @@ -230,7 +254,7 @@ void dump_pt_walk(paddr_t ttbr, paddr_t addr,
>      else
>          root_table = 0;
>  
> -    mapping = map_domain_page(mfn_add(root_mfn, root_table));
> +    mapping = xen_map_table(mfn_add(root_mfn, root_table));
>  
>      for ( level = root_level; ; level++ )
>      {
> @@ -246,11 +270,11 @@ void dump_pt_walk(paddr_t ttbr, paddr_t addr,
>              break;
>  
>          /* For next iteration */
> -        unmap_domain_page(mapping);
> -        mapping = map_domain_page(lpae_get_mfn(pte));
> +        xen_unmap_table(mapping);
> +        mapping = xen_map_table(lpae_get_mfn(pte));
>      }
>  
> -    unmap_domain_page(mapping);
> +    xen_unmap_table(mapping);
>  }
>  
>  void dump_hyp_walk(vaddr_t addr)
> @@ -713,30 +737,6 @@ void *ioremap(paddr_t pa, size_t len)
>      return ioremap_attr(pa, len, PAGE_HYPERVISOR_NOCACHE);
>  }
>  
> -static lpae_t *xen_map_table(mfn_t mfn)
> -{
> -    /*
> -     * During early boot, map_domain_page() may be unusable. Use the
> -     * PMAP to map temporarily a page-table.
> -     */
> -    if ( system_state == SYS_STATE_early_boot )
> -        return pmap_map(mfn);
> -
> -    return map_domain_page(mfn);
> -}
> -
> -static void xen_unmap_table(const lpae_t *table)
> -{
> -    /*
> -     * During early boot, xen_map_table() will not use map_domain_page()
> -     * but the PMAP.
> -     */
> -    if ( system_state == SYS_STATE_early_boot )
> -        pmap_unmap(table);
> -    else
> -        unmap_domain_page(table);
> -}
> -
>  static int create_xen_table(lpae_t *entry)
>  {
>      mfn_t mfn;
> -- 
> 2.38.1
>