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RE: [v2 1/4] xen/arm64: head: Don't map too much in boot_third
- To: Julien Grall <julien@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Henry Wang <Henry.Wang@xxxxxxx>
- Date: Thu, 29 Jun 2023 22:52:58 +0000
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- Cc: Luca Fancellu <Luca.Fancellu@xxxxxxx>, "michal.orzel@xxxxxxx" <michal.orzel@xxxxxxx>, Julien Grall <jgrall@xxxxxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>, "sstabellini@xxxxxxxxxx" <sstabellini@xxxxxxxxxx>
- Delivery-date: Thu, 29 Jun 2023 22:54:00 +0000
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- Thread-topic: [v2 1/4] xen/arm64: head: Don't map too much in boot_third
Hi Julien,
> -----Original Message-----
> Subject: [v2 1/4] xen/arm64: head: Don't map too much in boot_third
>
> From: Julien Grall <jgrall@xxxxxxxxxx>
>
> 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@xxxxxxxxxx>
Reviewed-by: Henry Wang <Henry.Wang@xxxxxxx>
Kind regards,
Henry
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