Re: [v2 1/4] xen/arm64: head: Don't map too much in boot_third

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>
Subject: Re: [v2 1/4] xen/arm64: head: Don't map too much in boot_third
Date: Fri, 30 Jun 2023 08:50:22 +0200	[thread overview]
Message-ID: <ad88adc9-5b05-65f9-2071-c746748ec3df@amd.com> (raw)
In-Reply-To: <20230629201129.12934-2-julien@xen.org>


On 29/06/2023 22:11, Julien Grall wrote:
> 
> 
> From: Julien Grall <jgrall@amazon.com>
> 
> At the moment, we are mapping the size of the reserved area for Xen
> (i.e. 2MB) even if the binary is smaller. We don't exactly know what's
> after Xen, so it is not a good idea to map more than necessary for a
> couple of reasons:
>     * We would need to use break-before-make if the extra PTE needs to
>       be updated to point to another region
>     * The extra area mapped may be mapped again by Xen with different
>       memory attribute. This would result to attribute mismatch.
> 
> Therefore, rework the logic in create_page_tables() to map only what's
> necessary. To simplify the logic, we also want to make sure _end
> is page-aligned. So align the symbol in the linker and add an assert
> to catch any change.
> 
> Lastly, take the opportunity to confirm that _start is equal to
> XEN_VIRT_START as the assembly is using both interchangeably.
> 
> Signed-off-by: Julien Grall <jgrall@amazon.com>
NIT: it looks like other maintainers are not CCed on this series.

Reviewed-by: Michal Orzel <michal.orzel@amd.com>

~Michal