Re: [RFC for-4.8 v2 1/7] xen/arm: Add MATTR_MEM_NC for normal non-cacheable memory

[Julien Grall <julien.grall@arm.com>]

Hi Edgar,

On 03/06/16 14:29, Edgar E. Iglesias wrote:
> From: "Edgar E. Iglesias" <edgar.iglesias@xilinx.com>
>
> Add the MATTR_MEM_NC macro describing normal non-cacheable memory.
>
> Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
> ---
>   xen/arch/arm/p2m.c         | 1 +
>   xen/include/asm-arm/page.h | 1 +
>   2 files changed, 2 insertions(+)
>
> diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
> index 838d004..0f1e1b1 100644
> --- a/xen/arch/arm/p2m.c
> +++ b/xen/arch/arm/p2m.c
> @@ -343,6 +343,7 @@ static lpae_t mfn_to_p2m_entry(unsigned long mfn, unsigned int mattr,
>           e.p2m.sh = LPAE_SH_INNER;
>           break;
>
> +    case MATTR_MEM_NC:

I would add a comment here to explain why non-cacheable memory should 
always be outer-shareable (see DDI 0406C.b B3-1376 to 1377).

For ideas on what to write, see mfn_to_xen_entry in include/asm-arm/page.h

>       case MATTR_DEV:
>           e.p2m.sh = LPAE_SH_OUTER;
>           break;
> diff --git a/xen/include/asm-arm/page.h b/xen/include/asm-arm/page.h
> index a94e978..45d2e2c 100644
> --- a/xen/include/asm-arm/page.h
> +++ b/xen/include/asm-arm/page.h
> @@ -73,6 +73,7 @@
>    *
>    */
>   #define MATTR_DEV     0x1
> +#define MATTR_MEM_NC  0x5
>   #define MATTR_MEM     0xf
>
>   /* Flags for get_page_from_gva, gvirt_to_maddr etc */
>

Regards,

-- 
Julien Grall

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