Re: [PATCH 8/9] xen/arm: Allow the user to build Xen with USBAN

From: Michal Orzel <michal.orzel@amd.com>
To: Julien Grall <julien@xen.org>, <xen-devel@lists.xenproject.org>
Cc: <Luca.Fancellu@arm.com>, <Henry.Wang@arm.com>,
	Julien Grall <jgrall@amazon.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	Bertrand Marquis <bertrand.marquis@arm.com>,
	Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
Subject: Re: [PATCH 8/9] xen/arm: Allow the user to build Xen with USBAN
Date: Mon, 26 Jun 2023 13:56:34 +0200	[thread overview]
Message-ID: <804682ce-ad88-34dc-1501-c9ff6347fb8b@amd.com> (raw)
In-Reply-To: <20230625204907.57291-9-julien@xen.org>


On 25/06/2023 22:49, Julien Grall wrote:
> 
> 
> From: Julien Grall <jgrall@amazon.com>
> 
> UBSAN has been enabled a few years ago on x86 but was never
> enabled on Arm because the final binary is bigger than 2MB (
> the maximum we can currently handled).
> 
> With the recent rework, it is now possible to grow Xen over 2MB.
> So there is no more roadblock to enable Xen other than increasing
> the reserved area.
> 
> On my setup, for arm32, the final binaray was very close to 4MB.
> Furthermore, one may want to enable USBAN and GCOV which would put
> the binary well-over 4MB (both features require for some space).
> Therefore, increase the size to 8MB which should us some margin.
> 
> Signed-off-by: Julien Grall <jgrall@amazon.com>
> 
> ----
> 
> The drawback with this approach is that we are adding 6 new
> page-table (3 for boot and 3 for runtime) that are statically
> allocated. So the final Xen binary will be 24KB bigger when
> neither UBSAN nor GCOV.
> 
> If this is not considered acceptable, then we could make the
> size of configurable in the Kconfig and decide it based on the
> features enabled.
Both of these features are enabled only in a debug build of Xen, so
another option would be to increase Xen size only for a debug build.

~Michal