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Re: [PATCH v2 5/6] arm/mpu: Implement early_fdt_map support in MPU systems

To: "Orzel, Michal" <michal.orzel@xxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>

From: Hari Limaye <Hari.Limaye@xxxxxxx>

Date: Fri, 11 Jul 2025 06:05:50 +0000

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Cc: Luca Fancellu <Luca.Fancellu@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>

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Thread-topic: [PATCH v2 5/6] arm/mpu: Implement early_fdt_map support in MPU systems

Hi Michal,

Thank you for reviewing the patch. To answer the following question:

> > + /* DTB starting at this address has already been mapped. */

> When can this happen?

In xen/arch/arm/setup.c `start_xen` early_fdt_map(fdt_paddr) is called twice,

before and after `setup_page_tables` - which is a no-op on an MPU system. This

seemed like the neatest way to handle this - but maybe you'd prefer further

clarification in the comment here?

Many thanks,

Hari