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Re: [Qemu-devel] [PATCH V2 RFC] fixup! virtio: convert to use DMA api
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH V2 RFC] fixup! virtio: convert to use DMA api |
Date: |
Wed, 27 Apr 2016 21:17:57 +0300 |
On Wed, Apr 27, 2016 at 04:15:35PM +0100, David Woodhouse wrote:
> 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.
The reasons for virtio are mostly dealing legacy.
We don't need protection is a separate issue
that I'd rather drop for now.
> > 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.
No one came up with a better one so far :(
> --
> dwmw2
- Re: [Qemu-devel] [PATCH V2 RFC] fixup! virtio: convert to use DMA api, (continued)
- Re: [Qemu-devel] [PATCH V2 RFC] fixup! virtio: convert to use DMA api, Michael S. Tsirkin, 2016/04/27
- Re: [Qemu-devel] [PATCH V2 RFC] fixup! virtio: convert to use DMA api, Andy Lutomirski, 2016/04/27
- Re: [Qemu-devel] [PATCH V2 RFC] fixup! virtio: convert to use DMA api, Michael S. Tsirkin, 2016/04/27
- Re: [Qemu-devel] [PATCH V2 RFC] fixup! virtio: convert to use DMA api, Joerg Roedel, 2016/04/27
- Re: [Qemu-devel] [PATCH V2 RFC] fixup! virtio: convert to use DMA api, Michael S. Tsirkin, 2016/04/27
- Re: [Qemu-devel] [PATCH V2 RFC] fixup! virtio: convert to use DMA api, Andy Lutomirski, 2016/04/27
- Re: [Qemu-devel] [PATCH V2 RFC] fixup! virtio: convert to use DMA api, Michael S. Tsirkin, 2016/04/27
- Re: [Qemu-devel] [PATCH V2 RFC] fixup! virtio: convert to use DMA api, Joerg Roedel, 2016/04/27
- Re: [Qemu-devel] [PATCH V2 RFC] fixup! virtio: convert to use DMA api, Michael S. Tsirkin, 2016/04/27
- Re: [Qemu-devel] [PATCH V2 RFC] fixup! virtio: convert to use DMA api, David Woodhouse, 2016/04/27
- Re: [Qemu-devel] [PATCH V2 RFC] fixup! virtio: convert to use DMA api,
Michael S. Tsirkin <=
- Re: [Qemu-devel] [PATCH V2 RFC] fixup! virtio: convert to use DMA api, David Woodhouse, 2016/04/27
- Re: [Qemu-devel] [PATCH V2 RFC] fixup! virtio: convert to use DMA api, Michael S. Tsirkin, 2016/04/28
- Re: [Qemu-devel] [PATCH V2 RFC] fixup! virtio: convert to use DMA api, David Woodhouse, 2016/04/28
- Re: [Qemu-devel] [PATCH V2 RFC] fixup! virtio: convert to use DMA api, Michael S. Tsirkin, 2016/04/28
- Re: [Qemu-devel] [PATCH V2 RFC] fixup! virtio: convert to use DMA api, David Woodhouse, 2016/04/28
Re: [Qemu-devel] [PATCH V2 RFC] fixup! virtio: convert to use DMA api, Stefan Hajnoczi, 2016/04/21