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RE: [PATCH 21/22] xen/arm64: Implement a mapcache for arm64
- To: Julien Grall <julien@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Henry Wang <Henry.Wang@xxxxxxx>
- Date: Fri, 6 Jan 2023 14:55:05 +0000
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- Cc: Julien Grall <jgrall@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- Delivery-date: Fri, 06 Jan 2023 14:55:23 +0000
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- Thread-topic: [PATCH 21/22] xen/arm64: Implement a mapcache for arm64
Hi Julien,
> -----Original Message-----
> Subject: [PATCH 21/22] xen/arm64: Implement a mapcache for arm64
>
> From: Julien Grall <jgrall@xxxxxxxxxx>
>
> At the moment, on arm64, map_domain_page() is implemented using
> virt_to_mfn(). Therefore it is relying on the directmap.
>
> In a follow-up patch, we will allow the admin to remove the directmap.
> Therefore we want to implement a mapcache.
>
> Thanksfully there is already one for arm32. So select
> ARCH_ARM_DOMAIN_PAGE
> and add the necessary boiler plate to support 64-bit:
> - The page-table start at level 0, so we need to allocate the level
> 1 page-table
> - map_domain_page() should check if the page is in the directmap. If
> yes, then use virt_to_mfn() to limit the performance impact
> when the directmap is still enabled (this will be selectable
> on the command line).
>
> Take the opportunity to replace first_table_offset(...) with offsets[...].
>
> Note that, so far, arch_mfns_in_directmap() always return true on
Nit: s/return/returns/
> arm64. So the mapcache is not yet used. This will change in a
> follow-up patch.
>
> Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
Reviewed-by: Henry Wang <Henry.Wang@xxxxxxx>
Kind regards,
Henry
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