Re: [Xen-devel] [PATCH v2 1/1] xen/arm: map_domain_page: reuse slots with avail == 0

[Tim Deegan <tim@xxxxxxx>]

At 13:06 +0100 on 30 Sep (1380546372), Stefano Stabellini wrote:
> If a slot has avail == 0 but still points to the right mfn, reuse it.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>

Acked-by: Tim Deegan <tim@xxxxxxx>

> Changes in v2:
> - check that the slot which we are about to reuse is valid.
> ---
>  xen/arch/arm/mm.c |   17 ++++++++++-------
>  1 files changed, 10 insertions(+), 7 deletions(-)
> 
> diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
> index 44ec0e3..21e20fa 100644
> --- a/xen/arch/arm/mm.c
> +++ b/xen/arch/arm/mm.c
> @@ -232,7 +232,15 @@ void *map_domain_page(unsigned long mfn)
>            i < DOMHEAP_ENTRIES;
>            slot = (slot + 1) % DOMHEAP_ENTRIES, i++ )
>      {
> -        if ( map[slot].pt.avail == 0 )
> +        if ( map[slot].pt.avail < 0xf &&
> +             map[slot].pt.base == slot_mfn &&
> +             map[slot].pt.valid )
> +        {
> +            /* This slot already points to the right place; reuse it */
> +            map[slot].pt.avail++;
> +            break;
> +        }
> +        else if ( map[slot].pt.avail == 0 )
>          {
>              /* Commandeer this 2MB slot */
>              pte = mfn_to_xen_entry(slot_mfn);
> @@ -240,12 +248,7 @@ void *map_domain_page(unsigned long mfn)
>              write_pte(map + slot, pte);
>              break;
>          }
> -        else if ( map[slot].pt.avail < 0xf && map[slot].pt.base == slot_mfn )
> -        {
> -            /* This slot already points to the right place; reuse it */
> -            map[slot].pt.avail++;
> -            break;
> -        }
> +
>      }
>      /* If the map fills up, the callers have misbehaved. */
>      BUG_ON(i == DOMHEAP_ENTRIES);
> -- 
> 1.7.2.5
> 

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