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Date:   Wed, 6 Apr 2022 17:47:23 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Jason Gunthorpe <jgg@nvidia.com>
Cc:     Christoph Hellwig <hch@lst.de>,
        Alex Williamson <alex.williamson@redhat.com>,
        Lu Baolu <baolu.lu@linux.intel.com>,
        Christian Benvenuti <benve@cisco.com>,
        Cornelia Huck <cohuck@redhat.com>,
        David Woodhouse <dwmw2@infradead.org>,
        Gerald Schaefer <gerald.schaefer@linux.ibm.com>,
        iommu@lists.linux-foundation.org, Jason Wang <jasowang@redhat.com>,
        Joerg Roedel <joro@8bytes.org>, kvm@vger.kernel.org,
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        linux-s390@vger.kernel.org,
        Matthew Rosato <mjrosato@linux.ibm.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Nelson Escobar <neescoba@cisco.com>, netdev@vger.kernel.org,
        Rob Clark <robdclark@gmail.com>,
        Robin Murphy <robin.murphy@arm.com>,
        Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
        virtualization@lists.linux-foundation.org,
        Will Deacon <will@kernel.org>,
        "Tian, Kevin" <kevin.tian@intel.com>
Subject: Re: [PATCH 1/5] iommu: Replace uses of IOMMU_CAP_CACHE_COHERENCY
 with dev_is_dma_coherent()
Message-ID: <20220406154723.GA30153@lst.de>
References: <0-v1-ef02c60ddb76+12ca2-intel_no_snoop_jgg@nvidia.com> <1-v1-ef02c60ddb76+12ca2-intel_no_snoop_jgg@nvidia.com> <20220406053039.GA10580@lst.de> <20220406120730.GA2120790@nvidia.com> <20220406135150.GA21532@lst.de> <20220406141446.GE2120790@nvidia.com>
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On Wed, Apr 06, 2022 at 11:14:46AM -0300, Jason Gunthorpe wrote:
> Really? It is the only condition that dma_info_to_prot() tests to
> decide of IOMMU_CACHE is used or not, so you are saying that there is
> a condition where a device can be attached to an iommu_domain and
> dev_is_dma_coherent() returns the wrong information? How does
> dma-iommu.c safely use it then?

arm does not use dma-iommu.c