Re: [Xen-devel] [RFC 11/22] xen/arm: p2m: Introduce p2m_get_root_pointer and use it in __p2m_lookup

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Thu, 28 Jul 2016, Julien Grall wrote:
> Mapping the root table is always done the same way. To avoid duplicating
> the code in a later patch, move the code in a separate helper.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxx>

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


>  xen/arch/arm/p2m.c | 53 +++++++++++++++++++++++++++++++++++------------------
>  1 file changed, 35 insertions(+), 18 deletions(-)
> 
> diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
> index ea582c8..d4a4b62 100644
> --- a/xen/arch/arm/p2m.c
> +++ b/xen/arch/arm/p2m.c
> @@ -204,6 +204,37 @@ static void p2m_flush_tlb_sync(struct p2m_domain *p2m)
>  }
>  
>  /*
> + * Find and map the root page table. The caller is responsible for
> + * unmapping the table.
> + *
> + * The function will return NULL if the offset of the root table is
> + * invalid.
> + */
> +static lpae_t *p2m_get_root_pointer(struct p2m_domain *p2m,
> +                                    gfn_t gfn)
> +{
> +    unsigned int root_table;
> +
> +    if ( P2M_ROOT_PAGES == 1 )
> +        return __map_domain_page(p2m->root);
> +
> +    /*
> +     * Concatenated root-level tables. The table number will be the
> +     * offset at the previous level. It is not possible to
> +     * concatenate a level-0 root.
> +     */
> +    ASSERT(P2M_ROOT_LEVEL > 0);
> +
> +    root_table = gfn_x(gfn) >>  (level_shifts[P2M_ROOT_LEVEL - 1] - 
> PAGE_SHIFT);
> +    root_table &= LPAE_ENTRY_MASK;
> +
> +    if ( root_table >= P2M_ROOT_PAGES )
> +        return NULL;
> +
> +    return __map_domain_page(p2m->root + root_table);
> +}
> +
> +/*
>   * Lookup the MFN corresponding to a domain's GFN.
>   *
>   * There are no processor functions to do a stage 2 only lookup therefore we
> @@ -226,7 +257,7 @@ static mfn_t __p2m_lookup(struct domain *d, gfn_t gfn, 
> p2m_type_t *t)
>      mfn_t mfn = INVALID_MFN;
>      paddr_t mask = 0;
>      p2m_type_t _t;
> -    unsigned int level, root_table;
> +    unsigned int level;
>  
>      ASSERT(p2m_is_locked(p2m));
>      BUILD_BUG_ON(THIRD_MASK != PAGE_MASK);
> @@ -236,22 +267,9 @@ static mfn_t __p2m_lookup(struct domain *d, gfn_t gfn, 
> p2m_type_t *t)
>  
>      *t = p2m_invalid;
>  
> -    if ( P2M_ROOT_PAGES > 1 )
> -    {
> -        /*
> -         * Concatenated root-level tables. The table number will be
> -         * the offset at the previous level. It is not possible to
> -         * concatenate a level-0 root.
> -         */
> -        ASSERT(P2M_ROOT_LEVEL > 0);
> -        root_table = offsets[P2M_ROOT_LEVEL - 1];
> -        if ( root_table >= P2M_ROOT_PAGES )
> -            goto err;
> -    }
> -    else
> -        root_table = 0;
> -
> -    map = __map_domain_page(p2m->root + root_table);
> +    map = p2m_get_root_pointer(p2m, gfn);
> +    if ( !map )
> +        return INVALID_MFN;
>  
>      ASSERT(P2M_ROOT_LEVEL < 4);
>  
> @@ -286,7 +304,6 @@ static mfn_t __p2m_lookup(struct domain *d, gfn_t gfn, 
> p2m_type_t *t)
>          *t = pte.p2m.type;
>      }
>  
> -err:
>      return mfn;
>  }
>  
> -- 
> 1.9.1
> 

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