Re: [PATCH 08/36] xen/arm: add colored flag to page struct

[Julien Grall <julien@xxxxxxx>]

Hi,

On 04/03/2022 17:46, Marco Solieri wrote:
> From: Luca Miccio <lucmiccio@xxxxxxxxx>
>
> A new allocator enforcing a cache-coloring configuration is going to be
> introduced.  We thus need to distinguish the memory pages assigned to,
> and managed by, such colored allocator from the ordinary buddy
> allocator's ones.  Add a color flag to the page structure.
>
> Signed-off-by: Luca Miccio <lucmiccio@xxxxxxxxx>
> Signed-off-by: Marco Solieri <marco.solieri@xxxxxxxxxxxxxxx>
> ---
>   xen/arch/arm/include/asm/mm.h | 4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/xen/arch/arm/include/asm/mm.h b/xen/arch/arm/include/asm/mm.h
> index 487be7cf59..9ac1767595 100644
> --- a/xen/arch/arm/include/asm/mm.h
> +++ b/xen/arch/arm/include/asm/mm.h
> @@ -88,6 +88,10 @@ struct page_info
>            */
>           u32 tlbflush_timestamp;
>       };
> +
> +    /* Is page managed by the cache-colored allocator? */
> +    bool colored;
struct page_info is going to be used quite a lot. In fact, there is one 
per RAM page. So we need to avoid growing the structure.
For Arm64, there is a 4 bytes padding here. But for arm32, there are 
none. So the size will increase by another 8 bytes.
In this case, I would use a bit in count_info.

Cheers,

--
Julien Grall