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Subject: Re: [RFC] virtio: Use DMA MAP API for devices without an IOMMU
To:     virtualization@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org
References: <20180405105631.9514-1-khandual@linux.vnet.ibm.com>
Cc:     robh@kernel.org, aik@ozlabs.ru, jasowang@redhat.com,
        joe@perches.com, linuxppc-dev@lists.ozlabs.org,
        elfring@users.sourceforge.net, david@gibson.dropbear.id.au,
        "Michael S. Tsirkin" <mst@redhat.com>
From:   Anshuman Khandual <khandual@linux.vnet.ibm.com>
Date:   Thu, 5 Apr 2018 20:09:30 +0530
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On 04/05/2018 04:26 PM, Anshuman Khandual wrote:
> There are certian platforms which would like to use SWIOTLB based DMA API
> for bouncing purpose without actually requiring an IOMMU back end. But the
> virtio core does not allow such mechanism. Right now DMA MAP API is only
> selected for devices which have an IOMMU and then the QEMU/host back end
> will process all incoming SG buffer addresses as IOVA instead of simple
> GPA which is the case for simple bounce buffers after being processed with
> SWIOTLB API. To enable this usage, it introduces an architecture specific
> function which will just make virtio core front end select DMA operations
> structure.
> 
> Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>

+ "Michael S. Tsirkin" <mst@redhat.com>