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Re: [PATCH v2] xen/arm: Don't use copy_from_paddr for DTB relocation
- To: Luca Fancellu <luca.fancellu@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- From: "Orzel, Michal" <michal.orzel@xxxxxxx>
- Date: Wed, 26 Feb 2025 15:10:09 +0100
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- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- Delivery-date: Wed, 26 Feb 2025 14:10:22 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 26/02/2025 12:26, Luca Fancellu wrote:
>
>
> Currently the early stage of the Arm boot maps the DTB using
> early_fdt_map() using PAGE_HYPERVISOR_RO which is cacheable
> read-only memory, later during DTB relocation the function
> copy_from_paddr() is used to map pages in the same range on
> the fixmap but using PAGE_HYPERVISOR_WC which is non-cacheable
> read-write memory.
>
> The Arm specifications, ARM DDI0487L.a, section B2.11 "Mismatched
> memory attributes" discourage using mismatched attributes for
> aliases of the same location.
>
> Given that there is nothing preventing the relocation since the region
> is already mapped, fix that by open-coding copy_from_paddr inside
> relocate_fdt, without mapping on the fixmap.
>
> Signed-off-by: Luca Fancellu <luca.fancellu@xxxxxxx>
Acked-by: Michal Orzel <michal.orzel@xxxxxxx>
~Michal
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