Re: [libvirt-users] Using hostdev to plug a PCI-E host device into Q35 pcie-root port

19 Nov 2013

      Am 19.11.2013 14:51, schrieb Thomas Kuther:
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Am 19.11.2013 11:36, schrieb Laine Stump:
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On 11/15/2013 03:35 PM, Thomas Kuther wrote:
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Hello,
I'm trying to migrate a working qemu command line configuration to
libvirt.
The part I'm currently failing on is:
$ qemu-system-x86_64 -M Q35 ... -device vfio-pci,host=05:00.0,bus=pcie.0
The right way to translate this into libvirt XML seems to be using
<hostdev>, but I seem to be unable to plug it into the pcie-root port
This is how the interesting part looks like when I let "virsh edit"
generate an <address>
<controller type='pci' index='0' model='pcie-root'/>
    <controller type='pci' index='1' model='dmi-to-pci-bridge'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02'
function='0x0'/>
    </controller>
    <controller type='pci' index='2' model='pci-bridge'>
      <address type='pci' domain='0x0000' bus='0x01' slot='0x01'
function='0x0'/>
    </controller>
    [...]
    <hostdev mode='subsystem' type='pci' managed='yes'>
      <driver name='vfio'/>
      <source>
        <address domain='0x0000' bus='0x03' slot='0x00' function='0x0'/>
      </source>
      <address type='pci' domain='0x0000' bus='0x02' slot='0x06'
function='0x0'/>
    </hostdev>
    [...]
To my understanding, this will plug the host device into the
pci-bridge controller.
The guest OS doesn't boot with this and resets right after bios.
Ugh. That's very unfortunate. This is the first report I've heard of
something failing in such a bad way due to being plugged into a
pci-bridge slot; up until now I'd only heard that there is some extra
PCIe functionality that would be missing if a device was plugged into a
PCI slot vs. PCIe.
Can I ask what type of device this is?
It's a Marvell 88SE9172 SATA controller, here is the lspci -vvv
[...]
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The second one I'm trying to pass through is a Renesas uPD720201 USB 3.0
Host Controller, but first I wanted to get the SATA controller working
in libvirt. I will try to leave out the SATA controller and see what
happens with only the USB3 controller.
I tried to pass through only the USB 3 controller. The guest boots, but
the controller isn't really working (means: no mouse and keyboard)
Also tried again with above SATA controller just to verify, same result:
the guest resets right after bios, causing a bios-reset-bios-reset loop.

If it matters, the hosts runs vanilla 3.12 + libvirt-1.1.4 + qemu-1.6.1
...
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I'm wondering as I type if possibly we could relax the enforcement of
the "PCI only" rule such that we allow explicitly placing any device on
any type of bus, but only auto-assign to a plain PCI slot. That may be a
reasonable compromise until qemu has the required new device/controller
introspection info available.
I like the idea.
I _really_ like the idea meanwhile :)

~Thomas