Messages in this thread |  | | Date | Thu, 5 Apr 2018 17:54:40 +0300 | From | "Michael S. Tsirkin" <> | Subject | Re: [RFC] virtio: Use DMA MAP API for devices without an IOMMU |
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On Thu, Apr 05, 2018 at 08:09:30PM +0530, Anshuman Khandual wrote: > 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>
I'm confused by this.
static bool vring_use_dma_api(struct virtio_device *vdev) { if (!virtio_has_iommu_quirk(vdev)) return true;
Why doesn't setting VIRTIO_F_IOMMU_PLATFORM on the hypervisor side sufficient?
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