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RE: [PATCH 4/7] xen/arm: page: Consolidate write_pte() and clarify the documentation
- To: Julien Grall <julien@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Henry Wang <Henry.Wang@xxxxxxx>
- Date: Tue, 20 Jun 2023 03:07:01 +0000
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- Cc: Luca Fancellu <Luca.Fancellu@xxxxxxx>, "michal.orzel@xxxxxxx" <michal.orzel@xxxxxxx>, Julien Grall <jgrall@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
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- Thread-topic: [PATCH 4/7] xen/arm: page: Consolidate write_pte() and clarify the documentation
Hi Julien,
> -----Original Message-----
> Subject: [PATCH 4/7] xen/arm: page: Consolidate write_pte() and clarify the
> documentation
>
> From: Julien Grall <jgrall@xxxxxxxxxx>
>
> The implementation of write_pte() is pretty much the same on arm32
> and arm64. So it would be good to consolidate it as this would help
> to clarify the requirements when using the helper.
>
> Take the opportunity to switch from assembly to call macros. Note there
> is a difference on arm32 because the option was not specified. But this
> meant 'sy' (system wide).
>
> Futhermore, the requirements for the ISB is incomplete. Per the Arm Arm,
> (Armv7 DDI406C.d A3.8.3 and Armv8 DDI 0487J.a B2.3.12), DSB will only
> affect explicit accesses. So an ISB is necessary after DSB to ensure
> the completion. Having an ISB after each update to the page-tables is
> probably too much, so let the caller add the instruction when it is
> convenient.
>
> Lastly, the barrier in write_pte() may be too restrictive but I haven't
> yet find the proper section(s) in the Arm Arm.
>
> Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
Reviewed-by: Henry Wang <Henry.Wang@xxxxxxx>
I've also tested this patch on top of today's staging by our internal CI, and
this patch looks good, so:
Tested-by: Henry Wang <Henry.Wang@xxxxxxx>
Kind regards,
Henry
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