linux-kernel - Re: [Xen-devel] [PATCH 07/11] swiotlb-xen: provide a single page-coherent.h header

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Date:   Fri, 16 Aug 2019 23:40:43 +0100
From:   Julien Grall <julien.grall@....com>
To:     Christoph Hellwig <hch@....de>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:     xen-devel@...ts.xenproject.org, iommu@...ts.linux-foundation.org,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [Xen-devel] [PATCH 07/11] swiotlb-xen: provide a single
 page-coherent.h header

Hi,

On 8/16/19 2:00 PM, Christoph Hellwig wrote:
> Merge the various page-coherent.h files into a single one that either
> provides prototypes or stubs depending on the need for cache
> maintainance.
> 
> For extra benefits alo include <xen/page-coherent.h> in the file
> actually implementing the interfaces provided.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>   arch/arm/include/asm/xen/page-coherent.h   |  2 --
>   arch/arm/xen/mm.c                          |  1 +
>   arch/arm64/include/asm/xen/page-coherent.h |  2 --
>   arch/x86/include/asm/xen/page-coherent.h   | 22 ------------------
>   drivers/xen/swiotlb-xen.c                  |  4 +---
>   include/Kbuild                             |  2 +-
>   include/xen/{arm => }/page-coherent.h      | 27 +++++++++++++++++++---

I am not sure I agree with this rename. The implementation of the 
helpers are very Arm specific as this is assuming Dom0 is 1:1 mapped.

This was necessary due to the lack of IOMMU on Arm platforms back then.
But this is now a pain to get rid of it on newer platform...

Cheers,

-- 
Julien Grall