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Date:   Wed, 13 Apr 2022 18:44:15 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Robin Murphy <robin.murphy@arm.com>
Cc:     Christoph Hellwig <hch@lst.de>, Chao Gao <chao.gao@intel.com>,
        linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
        m.szyprowski@samsung.com,
        Wang Zhaoyang1 <zhaoyang1.wang@intel.com>,
        Gao Liang <liang.gao@intel.com>,
        Kevin Tian <kevin.tian@intel.com>
Subject: Re: [PATCH] dma-direct: avoid redundant memory sync for swiotlb
Message-ID: <20220413164415.GA31640@lst.de>
References: <20220412113805.3210-1-chao.gao@intel.com> <e25fbb7e-a67e-5421-b7be-700fd0209b0d@arm.com> <20220413010157.GA10502@gao-cwp> <20220413045958.GA31209@lst.de> <4a993382-6a29-a0f4-4600-90ab60ad982a@arm.com>
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On Wed, Apr 13, 2022 at 02:10:56PM +0100, Robin Murphy wrote:
> Are you sure? AFAICS swiotlb_map() does the right thing, and 
> dma_direct_{sync,unmap} are working off the DMA address, which is that of 
> the bounce slot when SWIOTLB is involved (not least, how would the 
> is_swiotlb_buffer() checks work otherwise?)

Yeah, actually this should be fine.