Re: [PATCH for-4.19 v2] docs/arm: Document where Xen should be loaded in memory

[Bertrand Marquis <Bertrand.Marquis@xxxxxxx>]

Hi Julien,

> On 24 Oct 2023, at 12:28, Julien Grall <julien@xxxxxxx> wrote:
> 
> From: Julien Grall <jgrall@xxxxxxxxxx>
> 
> In commit 9d267c049d92 ("xen/arm64: Rework the memory layout"),
> we decided to require Xen to be loaded below 2 TiB to simplify
> the logic to enable the MMU. The limit was decided based on
> how known platform boot plus some slack.
> 
> We had a recent report that this is not sufficient on the AVA
> platform with a old firmware [1]. But the restriction is not
> going to change in Xen 4.18. So document the limit clearly
> in docs/misc/arm/booting.txt.
> 
> [1] https://lore.kernel.org/20231013122658.1270506-3-leo.yan@xxxxxxxxxx
> 
> Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
> Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>

Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>

Cheers
Bertrand

> 
> ---
> 
>    Changes in v2:
>        - The limit is 2 TiB no 5
>        - Remove unnecessary sentence in the docs
>        - Add missing link
>        - Add Michal's reviewed-by
> 
> I couldn't find a nice way to document it in SUPPORT.md. So I decided
> to only document the restrict in docs/misc/arm/booting.txt for now.
> 
> I also couldn't find any way from GRUB/UEFI (I didn't look much) to
> specify the loading address.
> ---
> docs/misc/arm/booting.txt | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/docs/misc/arm/booting.txt b/docs/misc/arm/booting.txt
> index 02f7bb65ec6d..547f58a7d981 100644
> --- a/docs/misc/arm/booting.txt
> +++ b/docs/misc/arm/booting.txt
> @@ -21,7 +21,9 @@ The exceptions to this on 32-bit ARM are as follows:
>  zImage protocol should still be used and not the stricter "raw
>  (non-zImage)" protocol described in arm/Booting.
> 
> -There are no exception on 64-bit ARM.
> +The exceptions to this on 64-bit ARM are as follows:
> +
> + Xen binary should be loaded in memory below 2 TiB.
> 
> Booting Guests
> --------------
> -- 
> 2.40.1
>