Messages in this thread | | | Date | Thu, 08 Nov 2007 09:06:19 -0600 | From | Anthony Liguori <> | Subject | Re: [kvm-devel] [PATCH 3/3] virtio PCI device |
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Avi Kivity wrote: > If a pci device is capable of dma (or issuing interrupts), it will be > useless with pv pci.
Hrm, I think we may be talking about different things. Are you thinking that the driver I posted allows you to do PCI pass-through over virtio? That's not what it is.
The driver I posted is a virtio implementation that uses a PCI device. This lets you use virtio-blk and virtio-net under KVM. The alternative to this virtio PCI device would be a virtio transport built with hypercalls like lguest has. I choose a PCI device because it ensured that each virtio device showed up like a normal PCI device.
Am I misunderstanding what you're asking about?
Regards,
Anthony Liguori
> >>> I think that with Amit's pvdma patches you >>> can support dma-capable devices as well without too much fuss. >>> >> >> What is the use case you're thinking of? A semi-paravirt driver that >> does dma directly to a device? > > No, an unmodified driver that, by using clever tricks with dma_ops, > can do dma directly to guest memory. See Amit's patches. > > In fact, why do a virtio transport at all? It can be done either with > trap'n'emulate, or by directly mapping the device mmio space into the > guest. > > > (what use case are you considering? devices without interrupts and > dma? pci door stoppers?) >
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