Re: [PATCH v3 09/19] xen/arm32: mm: Check if the virtual address is shared before updating it

[Julien Grall <julien@xxxxxxx>]

Hi,

On 21/02/2022 10:22, Julien Grall wrote:
> From: Julien Grall <jgrall@xxxxxxxxxx>
>
> Only the first 2GB of the virtual address space is shared between all
> the page-tables on Arm32.
>
> There is a long outstanding TODO in xen_pt_update() stating that the
> function can only work with shared mapping. Nobody has ever called
> the function with private mapping, however as we add more callers
> there is a risk to mess things up.
>
> Introduce a new define to mark the end of the shared mappings and use
> it in xen_pt_update() to verify if the address is correct.
>
> Note that on Arm64, all the mappings are shared. Some compiler may
> complain about an always true check, so the new define is not introduced
> for arm64 and the code is protected with an #ifdef.
>
> Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
>
> ---
>      Changes in v2:
>          - New patch
> ---
>   xen/arch/arm/include/asm/config.h |  4 ++++
>   xen/arch/arm/mm.c                 | 11 +++++++++--
While I working on removing the identity mapping, I realized this patch 
is actually getting in my way for arm32. I am planning to have multiple 
region that are shared, but still a single unshared region (the domheap 
mapping area).
So I will rework the patch to check is the address is part of the 
unshared region.
I will drop the patch from the series and move it to the next one.

Cheers,

--
Julien Grall