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

From David Woodhouse <dwmw2@infradead.org>
Newsgroups linux.kernel
Subject Re: [PATCH RFC] fixup! virtio: convert to use DMA api
Date 2016-04-18 14:00 +0200
Message-ID <rpg0q-502-3@gated-at.bofh.it> (permalink)
References <rpfQK-4Ut-23@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Mon, 2016-04-18 at 14:47 +0300, Michael S. Tsirkin wrote:
> This adds a flag to enable/disable bypassing the IOMMU by
> virtio devices.

I'm still deeply unhappy with having this kind of hack in the virtio
code at all, as you know. Drivers should just use the DMA API and if
the *platform* wants to make it a no-op for a specific device, then it
can.

Remember, this isn't just virtio either. Don't we have *precisely* the
same issue with assigned PCI devices on a system with an emulated Intel
IOMMU? The assigned PCI devices aren't covered by the emulated IOMMU,
and the platform needs to know to bypass *those* too.

Now, we've had this conversation, and we accepted the hack in virtio
for now until the platforms (especially SPARC and Power IIRC) can get
their act together and make their DMA API implementations not broken.

But now you're adding this hack to the public API where we have to
support it for ever. Please, can't we avoid that?

-- 
dwmw2

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Thread

[PATCH RFC] fixup! virtio: convert to use DMA api "Michael S. Tsirkin" <mst@redhat.com> - 2016-04-18 13:50 +0200
  Re: [PATCH RFC] fixup! virtio: convert to use DMA api David Woodhouse <dwmw2@infradead.org> - 2016-04-18 14:00 +0200
    Re: [PATCH RFC] fixup! virtio: convert to use DMA api "Michael S. Tsirkin" <mst@redhat.com> - 2016-04-18 15:20 +0200
      Re: [PATCH RFC] fixup! virtio: convert to use DMA api David Woodhouse <dwmw2@infradead.org> - 2016-04-18 16:10 +0200
        Re: [PATCH RFC] fixup! virtio: convert to use DMA api "Michael S. Tsirkin" <mst@redhat.com> - 2016-04-18 16:30 +0200
          Re: [PATCH RFC] fixup! virtio: convert to use DMA api David Woodhouse <dwmw2@infradead.org> - 2016-04-18 17:30 +0200
            Re: [PATCH RFC] fixup! virtio: convert to use DMA api "Michael S. Tsirkin" <mst@redhat.com> - 2016-04-18 17:40 +0200
              Re: [PATCH RFC] fixup! virtio: convert to use DMA api David Woodhouse <dwmw2@infradead.org> - 2016-04-18 18:00 +0200
                Re: [PATCH RFC] fixup! virtio: convert to use DMA api "Michael S. Tsirkin" <mst@redhat.com> - 2016-04-18 18:30 +0200
                Re: [PATCH RFC] fixup! virtio: convert to use DMA api David Woodhouse <dwmw2@infradead.org> - 2016-04-18 20:30 +0200
                Re: [PATCH RFC] fixup! virtio: convert to use DMA api Andy Lutomirski <luto@amacapital.net> - 2016-04-18 21:30 +0200
                Re: [PATCH RFC] fixup! virtio: convert to use DMA api "Michael S. Tsirkin" <mst@redhat.com> - 2016-04-19 12:30 +0200
                Re: [PATCH RFC] fixup! virtio: convert to use DMA api Andy Lutomirski <luto@amacapital.net> - 2016-04-19 18:10 +0200
                Re: [PATCH RFC] fixup! virtio: convert to use DMA api "Michael S. Tsirkin" <mst@redhat.com> - 2016-04-19 18:10 +0200
                Re: [PATCH RFC] fixup! virtio: convert to use DMA api Andy Lutomirski <luto@amacapital.net> - 2016-04-19 18:20 +0200
                Re: [PATCH RFC] fixup! virtio: convert to use DMA api "Michael S. Tsirkin" <mst@redhat.com> - 2016-04-19 18:30 +0200
                Re: [PATCH RFC] fixup! virtio: convert to use DMA api David Woodhouse <dwmw2@infradead.org> - 2016-04-19 19:40 +0200
                Re: [PATCH RFC] fixup! virtio: convert to use DMA api "Michael S. Tsirkin" <mst@redhat.com> - 2016-04-19 20:00 +0200
                Re: [PATCH RFC] fixup! virtio: convert to use DMA api Andy Lutomirski <luto@amacapital.net> - 2016-04-19 20:10 +0200
                Re: [PATCH RFC] fixup! virtio: convert to use DMA api "Michael S. Tsirkin" <mst@redhat.com> - 2016-04-19 22:20 +0200
                Re: [PATCH RFC] fixup! virtio: convert to use DMA api Andy Lutomirski <luto@amacapital.net> - 2016-04-19 22:30 +0200
                Re: [PATCH RFC] fixup! virtio: convert to use DMA api "Michael S. Tsirkin" <mst@redhat.com> - 2016-04-19 23:00 +0200
                Re: [PATCH RFC] fixup! virtio: convert to use DMA api Andy Lutomirski <luto@amacapital.net> - 2016-04-19 23:10 +0200
                Re: [PATCH RFC] fixup! virtio: convert to use DMA api "Michael S. Tsirkin" <mst@redhat.com> - 2016-04-20 15:20 +0200
                Re: [PATCH RFC] fixup! virtio: convert to use DMA api Andy Lutomirski <luto@amacapital.net> - 2016-04-20 17:50 +0200
                Re: [PATCH RFC] fixup! virtio: convert to use DMA api "Michael S. Tsirkin" <mst@redhat.com> - 2016-04-19 11:20 +0200
                Re: [PATCH RFC] fixup! virtio: convert to use DMA api Alex Williamson <alex.williamson@redhat.com> - 2016-04-19 16:50 +0200
                Re: [PATCH RFC] fixup! virtio: convert to use DMA api Andy Lutomirski <luto@amacapital.net> - 2016-04-19 18:10 +0200
                Re: [PATCH RFC] fixup! virtio: convert to use DMA api "Michael S. Tsirkin" <mst@redhat.com> - 2016-04-19 18:10 +0200

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