linux-kernel - Re: [PATCH 3/9] iommu/dma-iommu: Add iommu_dma_copy_reserved_iova, iommu_dma_apply_resv

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Date:   Tue, 16 Apr 2019 14:37:39 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Tom Murphy <tmurphy@...sta.com>,
        Christoph Hellwig <hch@...radead.org>
Cc:     iommu@...ts.linux-foundation.org, Heiko Stuebner <heiko@...ech.de>,
        Will Deacon <will.deacon@....com>,
        David Brown <david.brown@...aro.org>,
        linux-samsung-soc@...r.kernel.org,
        Dmitry Safonov <dima@...sta.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        linux-rockchip@...ts.infradead.org, Kukjin Kim <kgene@...nel.org>,
        Andy Gross <andy.gross@...aro.org>,
        Marc Zyngier <marc.zyngier@....com>,
        linux-arm-msm@...r.kernel.org, linux-mediatek@...ts.infradead.org,
        Matthias Brugger <matthias.bgg@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Tom Murphy <murphyt7@....ie>
Subject: Re: [PATCH 3/9] iommu/dma-iommu: Add iommu_dma_copy_reserved_iova,
 iommu_dma_apply_resv_region to the dma-iommu api

On 16/04/2019 14:22, Tom Murphy wrote:
> I hoped this could be an exception, it's easier to grok without the
> line break and isn't crazy long. Because you mentioned it I'll fix it.

Frankly this patch is hard to justify anyway - iommu-dma already has its 
own reserved region handling, and there should be no need for external 
callers to be poking into the innards provided the IOMMU driver reports 
the correct reserved regions in the first place.

If the iommu-dma abstraction is not quite sufficient to actually convert 
amd-iommu to use it properly, then we should improve the abstraction, 
rather than just punching holes in it to merely poke renamed parts of 
the existing amd-iommu logic into.

Robin.

> On Mon, Apr 15, 2019 at 7:31 AM Christoph Hellwig <hch@...radead.org> wrote:
>>
>> On Thu, Apr 11, 2019 at 07:47:32PM +0100, Tom Murphy via iommu wrote:
>>> +
>>> +     WARN_ON_ONCE(iommu_dma_reserve_iova(domain, region->start, end) == NULL);
>>
>> Overly long line..