On 10.12.2009, at 11:56, Michael S. Tsirkin wrote: > On Thu, Dec 10, 2009 at 12:37:37PM +0200, Muli Ben-Yehuda wrote: >> On Thu, Dec 10, 2009 at 11:31:01AM +0100, Alexander Graf wrote: >> >>>> What do you have in mind for such a rewrite? >>> >>> I'd like to see it more well-abstracted and versatile. I don't see >>> an obvious reason why we shouldn't be able to use a physical device >>> in a TCG target :-). >> >> mmio and pio are easy, DMA you'd need an IOMMU for security, or >> whatever uio does just for translation, > > uio currently does not support DMA, but I plan to fix this > >> and interrupts you probably >> get for free from uio. Seems eminently doable to me. Why you'd want to >> is another matter :-) >> >> Cheers, >> Muli > > The list above ignores the biggest issue: you would have to change TCG > code generation to make this work. > > For example, I think a read memory barrier is currently ignored in > translation, and host CPU will reorder reads. Some drivers might also > rely on ordering guarantees that depend on CPU cacheline sizes. Atomics > is another bag of tricks but I expect atomics on a DMA memory are not > widely used. Since we'd use the mmio callbacks for MMIO we'd be strictly ordered, no? Alex -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
