On Mon, Jul 25, 2016 at 12:50:09AM -0700, Christoph Hellwig wrote: > On Tue, Jul 19, 2016 at 05:38:23AM +0300, Michael S. Tsirkin wrote: > > > > On other systems, including SPARC and PPC64, virtio-pci devices are > > enumerated as though they are behind an IOMMU, but the virtio host > > ignores the IOMMU, so we must either pretend that the IOMMU isn't > > there or somehow map everything as the identity. > > > > Add a feature bit to detect that quirk: VIRTIO_F_IOMMU_PLATFORM. > > > > Any device with this feature bit set to 0 needs a quirk and has to be > > passed physical addresses (as opposed to bus addresses) even though > > the device is behind an IOMMU. > > This is the wrong way around. Well given there are tons of quirky devices out there and they have this bit set to 0, I don't think we can change this. New devices will have it set to 1. > > Note: it has to be a per-device quirk because for example, there could > > be a mix of passed-through and virtual virtio devices. As another > > example, some devices could be implemented by an out of process > > hypervisor backend (in case of qemu vhost, or vhost-user) and so support > > for an IOMMU needs to be coded up separately. > > > > It would be cleanest to handle this in IOMMU core code, but that needs > > per-device DMA ops. While we are waiting for that to be implemented, use > > a work-around in virtio core. > > > > Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx> > > --- > > > > wanted to use per-device dma ops but that does not > > seem to be ready. So let's put this in virtio > > code for now, and move when it becomes possible. > > So work on making it ready. We're close to there, and given that > virtio needs it, finish it off. We now have everyone using the > operation vectors for DMA, so the only thing you need is a dma_ops > pointer in struct device initialized to what get_dma_ops returns. And then pci_dma_configure would have a quirk to set that for legacy virtio devices? -- MST _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
