Re: [PATCH v4 0/6] virtio core DMA API conversion

From	Benjamin Herrenschmidt <benh@kernel.crashing.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH v4 0/6] virtio core DMA API conversion
Date	2015-11-10 20:40 +0100
Message-ID	<qtmVR-Qu-27@gated-at.bofh.it> (permalink)
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On Tue, 2015-11-10 at 11:27 +0100, Joerg Roedel wrote:
> 
> You have the same problem when real PCIe devices appear that speak
> virtio. I think the only real (still not very nice) solution is to add a
> quirk to powerpc platform code that sets noop dma-ops for the existing
> virtio vendor/device-ids and add a DT property to opt-out of that quirk.
>
> New vendor/device-ids (as for real devices) would just not be covered by
> the quirk and existing emulated devices continue to work.

Why woud real devices use new vendor/device IDs ? Also there are other
cases such as using virtio between 2 partitions, which we could do
under PowerVM ... that would require proper iommu usage with existing
IDs.

> The absence of the property just means that the quirk is in place and
> the system assumes no translation for virtio devices.

The only way that works forward for me (and possibly sparc & others,
what about ARM ?) is if we *change* something in virtio qemu at the
same time as we add some kind of property. For example the ProgIf field
or revision ID field.

That way I can key on that change.

It's still tricky because I would have to somewhat tell my various firmwares
(SLOF, OpenBIOS, OPAL, ...) so they can create the appropriate property, it's
still hacky, but it would be workable.

Ben.

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Re: [PATCH v4 0/6] virtio core DMA API conversion "Michael S. Tsirkin" <mst@redhat.com> - 2015-11-09 13:20 +0100
  Re: [PATCH v4 0/6] virtio core DMA API conversion Paolo Bonzini <pbonzini@redhat.com> - 2015-11-09 13:30 +0100
  Re: [PATCH v4 0/6] virtio core DMA API conversion Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2015-11-10 00:30 +0100
    Re: [PATCH v4 0/6] virtio core DMA API conversion Andy Lutomirski <luto@amacapital.net> - 2015-11-10 01:50 +0100
      Re: [PATCH v4 0/6] virtio core DMA API conversion Andy Lutomirski <luto@amacapital.net> - 2015-11-10 03:20 +0100
        Re: [PATCH v4 0/6] virtio core DMA API conversion Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2015-11-10 06:30 +0100
          Re: [PATCH v4 0/6] virtio core DMA API conversion Andy Lutomirski <luto@amacapital.net> - 2015-11-10 06:40 +0100
            Re: [PATCH v4 0/6] virtio core DMA API conversion Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2015-11-10 11:40 +0100
              Re: [PATCH v4 0/6] virtio core DMA API conversion "Michael S. Tsirkin" <mst@redhat.com> - 2015-11-10 13:50 +0100
                Re: [PATCH v4 0/6] virtio core DMA API conversion Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2015-11-10 21:40 +0100
              Re: [PATCH v4 0/6] virtio core DMA API conversion Andy Lutomirski <luto@amacapital.net> - 2015-11-10 20:00 +0100
                Re: [PATCH v4 0/6] virtio core DMA API conversion Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2015-11-10 23:30 +0100
                Re: [PATCH v4 0/6] virtio core DMA API conversion Andy Lutomirski <luto@amacapital.net> - 2015-11-11 00:50 +0100
                Re: [PATCH v4 0/6] virtio core DMA API conversion Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2015-11-11 01:50 +0100
                Re: [PATCH v4 0/6] virtio core DMA API conversion Andy Lutomirski <luto@amacapital.net> - 2015-11-11 05:50 +0100
                Re: [PATCH v4 0/6] virtio core DMA API conversion Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2015-11-11 06:10 +0100
        Re: [PATCH v4 0/6] virtio core DMA API conversion Andy Lutomirski <luto@amacapital.net> - 2015-11-10 06:40 +0100
        Re: [PATCH v4 0/6] virtio core DMA API conversion Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2015-11-10 07:30 +0100
        Re: [PATCH v4 0/6] virtio core DMA API conversion Jan Kiszka <jan.kiszka@siemens.com> - 2015-11-10 09:20 +0100
      Re: [PATCH v4 0/6] virtio core DMA API conversion Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2015-11-10 04:10 +0100
        Re: [PATCH v4 0/6] virtio core DMA API conversion Knut Omang <knut.omang@oracle.com> - 2015-11-10 10:50 +0100
          Re: [PATCH v4 0/6] virtio core DMA API conversion Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2015-11-10 11:50 +0100
        Re: [PATCH v4 0/6] virtio core DMA API conversion Joerg Roedel <jroedel@suse.de> - 2015-11-10 11:30 +0100
          Re: [PATCH v4 0/6] virtio core DMA API conversion Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2015-11-10 20:40 +0100

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