Re: [PATCH v3 0/3] virtio DMA API core stuff

From: Andy Lutomirski
Date: Thu Nov 19 2015 - 16:59:31 EST

On Nov 19, 2015 5:45 AM, "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote:
> On Tue, Oct 27, 2015 at 11:38:57PM -0700, Andy Lutomirski wrote:
> > This switches virtio to use the DMA API unconditionally. I'm sure
> > it breaks things, but it seems to work on x86 using virtio-pci, with
> > and without Xen, and using both the modern 1.0 variant and the
> > legacy variant.
> So thinking hard about it, I don't see any real drawbacks to making this
> conditional on a new feature bit, that Xen can then set..

Can you elaborate? If I run QEMU, hosting Xen, hosting Linux, and the
virtio device is provided by QEMU, then how does Xen set the bit?
Similarly, how would Xen set the bit for a real physical device?

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