Messages in this thread | | | Date | Fri, 20 Nov 2015 08:56:46 +0200 | From | "Michael S. Tsirkin" <> | Subject | Re: [PATCH v3 0/3] virtio DMA API core stuff |
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On Thu, Nov 19, 2015 at 01:59:05PM -0800, Andy Lutomirski wrote: > On Nov 19, 2015 5:45 AM, "Michael S. Tsirkin" <mst@redhat.com> 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?
You would run QEMU with the appropriate flag. E.g. -global virtio-pci,use_platform_dma=on
> Similarly, how would Xen set the bit for a real physical device? > > > --Andy
There's no need to set bits for physical devices I think: from security point of view, using them from a VM isn't very different from using them from host.
-- MST
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