Re: [Xen-devel] [PATCH 13/15] xen/arm: p2m: Introduce a new variable removing_mapping in __p2m_set_entry

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 16 Jul 2018, Julien Grall wrote:
> This is making the code slightly easier to understand.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> ---
>  xen/arch/arm/p2m.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
> index 66d58fabd7..e826f57842 100644
> --- a/xen/arch/arm/p2m.c
> +++ b/xen/arch/arm/p2m.c
> @@ -792,6 +792,8 @@ static int __p2m_set_entry(struct p2m_domain *p2m,
>      unsigned int target = 3 - (page_order / LPAE_SHIFT);
>      lpae_t *entry, *table, orig_pte;
>      int rc;
> +    /* A mapping is removed if the MFN is invalid. */
> +    bool removing_mapping = mfn_eq(smfn, INVALID_MFN);
>  
>      /* Convenience aliases */
>      const unsigned int offsets[4] = {
> @@ -817,9 +819,9 @@ static int __p2m_set_entry(struct p2m_domain *p2m,
>      {
>          /*
>           * Don't try to allocate intermediate page table if the mapping
> -         * is about to be removed (i.e mfn == INVALID_MFN).
> +         * is about to be removed.
>           */
> -        rc = p2m_next_level(p2m, mfn_eq(smfn, INVALID_MFN),
> +        rc = p2m_next_level(p2m, removing_mapping,
>                              level, &table, offsets[level]);
>          if ( rc == GUEST_TABLE_MAP_FAILED )
>          {
> @@ -830,7 +832,7 @@ static int __p2m_set_entry(struct p2m_domain *p2m,
>               * when removing a mapping as it may not exist in the
>               * page table. In this case, just ignore it.
>               */
> -            rc = mfn_eq(smfn, INVALID_MFN) ? 0 : -ENOENT;
> +            rc = removing_mapping ?  0 : -ENOENT;
>              goto out;
>          }
>          else if ( rc != GUEST_TABLE_NORMAL_PAGE )
> @@ -925,7 +927,7 @@ static int __p2m_set_entry(struct p2m_domain *p2m,
>      if ( lpae_is_valid(orig_pte) )
>          p2m_remove_pte(entry, p2m->clean_pte);
>  
> -    if ( mfn_eq(smfn, INVALID_MFN) )
> +    if ( removing_mapping )
>          /* Flush can be deferred if the entry is removed */
>          p2m->need_flush |= !!lpae_is_valid(orig_pte);
>      else
> -- 
> 2.11.0
> 

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