linux-kernel - Re: [PATCH 2/9] dma-direct: reject highmem pages from dma_alloc_from

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Message-ID: <20181201165716.GB20912@lst.de>
Date:   Sat, 1 Dec 2018 17:57:16 +0100
From:   Christoph Hellwig <hch@....de>
To:     Robin Murphy <robin.murphy@....com>
Cc:     Christoph Hellwig <hch@....de>, iommu@...ts.linux-foundation.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>, Guo Ren <ren_guo@...ky.com>,
        Laura Abbott <labbott@...hat.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/9] dma-direct: reject highmem pages from
 dma_alloc_from_contiguous

On Fri, Nov 30, 2018 at 07:04:51PM +0000, Robin Murphy wrote:
> On 05/11/2018 12:19, Christoph Hellwig wrote:
>> dma_alloc_from_contiguous can return highmem pages depending on the
>> setup, which a plain non-remapping DMA allocator can't handle.  Detect
>> this case and try the normal page allocator instead.
>
> ...except the actual implementation is "Detect this case and fail the 
> entire allocation if so".

True, that actually changed from when I wrote the commit log due to
some layer issues.  I'll update the commit log.