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Re: [for-4.19] xen/arm64: head: only use the macro load_paddr() in the MMU code
- To: Julien Grall <julien@xxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Michal Orzel <michal.orzel@xxxxxxx>
- Date: Tue, 17 Oct 2023 16:07:17 +0200
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- Cc: <ayan.kumar.halder@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- Delivery-date: Tue, 17 Oct 2023 14:07:59 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
Hi Julien,
On 17/10/2023 14:52, Julien Grall wrote:
>
>
> The macro load_paddr() requires to know the offset between the
> physical location of Xen and the virtual location.
>
> When using the MPU, x20 will always be 0. Rather than wasting
> a register for a compile-time constant value, it would be best if
> we can avoid using load_paddr() altogher in the common head.S code.
s/altogher/altogether/
>
> The current use of load_paddr() are equivalent to adr_l() because
> the MMU is off.
>
> All the use of load_paddr() in arm64/head.S are now replaced with
> adr_l(). With that, load_paddr() can now be moved in arm64/mmu/head.S.
>
> For now, x20 is still unconditionally set. But this could change
> in the future if needed.
>
> Signed-off-by: Julien Grall <julien@xxxxxxx>
Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>
Side note:
Looking at all the uses of load_paddr(), none of them takes place after
enabling MMU
which would indicate that we actually don't need this macro at all. Do you
agree?
~Michal
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