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Re: [PATCH] xen/arm: mmu: avoid transient mapping of page tables when a directmap is available
- To: mixx86 <gabi.qs.mail@xxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 7 Jul 2026 08:36:54 +0200
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- Cc: sstabellini@xxxxxxxxxx, julien@xxxxxxx, bertrand.marquis@xxxxxxx, michal.orzel@xxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Tue, 07 Jul 2026 06:37:07 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 07.07.2026 00:29, mixx86 wrote:
> ---
> xen/arch/arm/mmu/pt.c | 13 +++++++++++--
> 1 file changed, 11 insertions(+), 2 deletions(-)
First two formal things: There's no S-o-b of yours, and a change like this
hardly can come with an empty description.
> --- a/xen/arch/arm/mmu/pt.c
> +++ b/xen/arch/arm/mmu/pt.c
> @@ -42,7 +42,11 @@ static lpae_t *xen_map_table(mfn_t mfn)
> if ( system_state == SYS_STATE_early_boot )
> return pmap_map(mfn);
>
> +#if defined(CONFIG_ARM_64)
> + return __va((mfn_to_maddr(mfn)));
> +#else
> return map_domain_page(mfn);
> +#endif
> }
The abstraction exists for a reason. If anything CONFIG_ARCH_MAP_DOMAIN_PAGE
would be the correct dependency here (or else the pattern, if copied
elsewhere, would break the MPU=y case), yet that already is what controls
whether map_domain_page() is a mapping operation in the first place.
Plus - why would only this call site benefit? Any improvement should be done
in map_domain_page() itself.
Jan
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