[PATCH V2 RFC] fixup! virtio: convert to use DMA api

David Woodhouse
Wed, 27 Apr 2016 15:15:35 -0000

On Wed, 2016-04-27 at 18:05 +0300, Michael S. Tsirkin
wrote:
>
> I really don't get it.
>
> There's exactly one device that works now and needs the work-around and
> so that we need to support, and that is virtio. It happens to have
> exactly the same issue on all platforms.

False. We have other devices which are currently *not* translated by
the emulated IOMMU and which aren't going to be in the short term
either.

We also have other devices (emulated hardware NICs) to which precisely
the same "we don't need protection" arguments apply, and which we
*could* expose to the guest without an IOMMU translation if we really
wanted to. It makes as much sense as exposing virtio without an IOMMU,
going forward.

> Why would we want to work hard to build platform-specific
> solutions to a problem that can be solved in 5 lines of
> generic code?

Because it's a dirty hack in the *wrong* place.

--
dwmw2
-------------- next part --------------
A non-text attachment was scrubbed...
Name: smime.p7s
Type: application/x-pkcs7-signature
Size: 5691 bytes
Desc: not available
URL:
<http://lists.linuxfoundation.org/pipermail/virtualization/attachments/20160427/a2174d1e/attachment.bin>