On Mon, 2016-04-18 at 14:47 +0300, Michael S. Tsirkin wrote: > This adds a flag to enable/disable bypassing the IOMMU by > virtio devices. I'm still deeply unhappy with having this kind of hack in the virtio code at all, as you know. Drivers should just use the DMA API and if the *platform* wants to make it a no-op for a specific device, then it can. Remember, this isn't just virtio either. Don't we have *precisely* the same issue with assigned PCI devices on a system with an emulated Intel IOMMU? The assigned PCI devices aren't covered by the emulated IOMMU, and the platform needs to know to bypass *those* too. Now, we've had this conversation, and we accepted the hack in virtio for now until the platforms (especially SPARC and Power IIRC) can get their act together and make their DMA API implementations not broken. But now you're adding this hack to the public API where we have to support it for ever. Please, can't we avoid that? -- dwmw2
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