On Wed, 2016-04-27 at 21:17 +0300, Michael S. Tsirkin wrote: > > > Because it's a dirty hack in the *wrong* place. > > No one came up with a better one so far :( Seriously? Take a look at drivers/iommu/intel-iommu.c. It has quirks for all kinds of shitty devices that have to be put in passthrough mode or otherwise excluded. We don't actually *need* it for the Intel IOMMU; all we need is for QEMU to stop lying in its DMAR tables. We *do* want the same kind of quirks in the relevant POWER and ARM IOMMU code in the kernel. Do that (hell, a simple quirk for all virtio devices will suffice, but NOT in the virtio driver) at the same moment you fix the virtio devices to use the DMA API. Job done. Some time *later* we can work on *refining* that quirk, and a way for QEMU to tell the guest (via something generic like fwcfg, maybe) that some devices are and aren't translated. Actually, I'm about to look at moving dma_ops into struct device and cleaning up the way we detect which IOMMU is attached, at device instantiation time. Perhaps I can shove the virtio-exception quirk in there while I'm at it... -- dwmw2
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