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<div class="moz-cite-prefix">On 2016-04-12 18:32, Alex Williamson
wrote:<br>
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<div>On 2016-04-12 17:24, Alex Williamson wrote:<br>
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<div class="gmail_quote"><span class="">On Tue,
Apr 12, 2016 at 2:30 PM, Bronek Kozicki <span
dir="ltr"><<a moz-do-not-send="true"
href="mailto:brok@spamcop.net"
target="_blank">brok@spamcop.net</a>></span>
wrote:<br>
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2. does PCI bridge have to be in a
separate IOMMU group than passed-through
device?<br>
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<div>No. Blank is mostly correct on this,
newer kernel remove the pcieport driver
test and presumes any driver attached to a
bridge device is ok.</div>
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Really? From what I understood reading your IOMMU
article, plus from the issues I had getting my own GPU
to work on the CPU-based PCIe slot on my E3-1200, I
thought having a PCIe root port grouped with a PCI
device made the GPU unsuited for passthrougs. What
reccomendations should I give <a
moz-do-not-send="true"
href="https://wiki.archlinux.org/index.php/PCI_passthrough_via_OVMF#Plugging_your_guest_GPU_in_an_unisolated_CPU-based_PCIe_slot"
target="_blank">here</a>, then?<br>
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<div>The statement "(there's generally only one)" is
completely incorrect regarding processor based root port
slots. That $30k PC that LinuxTechTips did has 7
processor based root ports between the 2 sockets.</div>
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You're right, I shouldn't have extrapolated from the fact that most
of the consumer hardware I have access to works that way, I'll
remove that line on my next edit.<br>
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<div>IOMMU group isolation requires that a group is never
shared between host and guest or between different
guests. However we assume that bridge devices only do DMA
on behalf of the devices downstream of them, so we allow
the bridge to be managed by a host driver. So in your
example, it's possible that the bridge could do
redirections, but the only affected party would be the VM
itself. The same is true for a multi-function device like
the GPU itself, internal routing may allow the devices to
perform peer-to-peer internally. So it's not ideal when
the bridge is part of the group, but it generally works
and is allowed because it can't interfere with anyone
else. </div>
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Ah, I see. I suppose the issues i was having with my 970 were due to
something else, then. Now that I look back at it, it's probably
because my CPU-based PCIe slot was <a
href="https://www.redhat.com/archives/vfio-users/2015-October/msg00005.html">the
only one that could be set as a boot GPU</a>. I'll try to rework
that part and mention that it adresses a much more specific case
than what I iniaially thought, then.<br>
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<div>I have the identical setup on my E3-1245v2 and haven't
had any problems.</div>
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The line is actually copy-pasted from your IOMMU blog-articles,
since my own machine no longer follows that configuration and I
needed a snippet for that specific exemple.<br>
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<div class="moz-cite-prefix">On 2016-04-12 18:57, Alex Williamson
wrote:<br>
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<div class="gmail_extra">Skimming...</div>
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<div class="gmail_extra">Most of those AMD CPUs in the <a
moz-do-not-send="true" href="http://amd.com">amd.com</a>
link do not support AMD-Vi</div>
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I should have double-checked, I was under the impression that RVI
and AMD-Vi were the same thing. The fact that AMD doesn't really
maintain any sort of public centralized database like Intel ARK
makes it really complicated to give advices on this.<br>
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<div class="gmail_extra">User-level access to devices... No,
don't do this. System mode libvirt manages device
permissions. If you want unprivileged, session mode libvirt
you need a whole other wiki page.<br>
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<div class="gmail_extra">Binding to VFIO... Gosh I wish those
vfio-bind scripts would die. Just use libvirt, virsh
nodedev-detach<br>
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<div class="gmail_extra">QEMU permissions... WRONG! Don't touch
any of this.<br>
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<div class="gmail_extra">Complete example for QEMU with
libvirtd... No, qemu:args are the worst. This hides the
assigned device from libvirt and is what causes you to need to
do the QEMU permissions hacks that are completely wrong. Use
a wrapper script!<br>
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<div class="gmail_extra">As others have said, ignore_msrs makes
lots of things work, not just GeForce Experience</div>
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Yeah, I think you're starting to see why a rewrite is in order here.
;)<br>
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