(Sorry: Pressed send too fast...)
3. I'm facing some odd memory allocation issues (only if the VM is Q35, all works well if the VM is configured as i440fx), which may require me to change additional VM parameters.

BTW, ironically, the two other hosts in the same cluster, with older MBs, have zero issues with GPU/Audio/USB passthrough...)

- Gilboa

On Tue, Nov 9, 2021 at 11:52 AM Gilboa Davara <gilboad@gmail.com> wrote:

Hello,

Many thanks for the prompt reply.

On Mon, Nov 8, 2021 at 8:52 PM Nir Soffer <nsoffer@redhat.com> wrote:

On Mon, Nov 8, 2021 at 5:47 PM Gilboa Davara <gilboad@gmail.com> wrote:
>
> Hello all,
>
> I'm setting up a fairly (?) complex oVirt over Gluster setup built around 3 Xeon servers-turned-into-workstations, each doubling as oVirt node + one primary Fedora VM w/ a dedicated passthrough GPU (+audio and a couple of USB root devices).
> One of the servers seems to have some weird issue w/ the passthrough nVidia GPU that seems to require me to edit the VM iommu (1) and passthrough device (2) command line.
> I tried using the qemu-cmdline addon to add the missing parameters, but it seems that qemu treats the added parameters as an additional device / iommu instead of editing the existing parameters.
>
> So:
> 1. How can I view the VM qemu command line?

less /var/log/libvirt/qemu/vm-name.log

Found it, thanks!

> 2. Can I somehow manually edit the qemu command line, either directly or by somehow adding parameters in the HE XML file?

I think this should be possible via vdsm hook, but hooks are bad.
Can you explain what do you want to change?

Nir

1. IOMMU:

-device intel-iommu,intremap=on,eim=on

To (Add: caching-mode=on, per qemu log message)

-device intel-iommu,intremap=on,eim=on,caching-mode=on

(2021-11-05T18:42:36.651191Z qemu-kvm: We need to set caching-mode=on for intel-iommu to enable device assignment with IOMMU protection.)

2. Device:

-device vfio-pci,host=0000:84:00.0,id=ua-c774115b-c0ee-43a5-97c8-12ac73cb6f3a,bus=pci.10,addr=0x0

-device vfio-pci,host=0000:84:00.1,id=ua-3c7d3b66-57aa-470b-afc8-78383ac9a025,bus=pci.8,addr=0x0

To (Attach hdmi sound as function of GPU, possibly add x-vga=on):

-device vfio-pci,host=0000:84:00.0,id=ua-c774115b-c0ee-43a5-97c8-12ac73cb6f3a,bus=pci.8.0,x-vga=on,addr=0x0

-device vfio-pci,host=0000:84:00.1,id=ua-3c7d3b66-57aa-470b-afc8-78383ac9a025,bus=pci.8.1,addr=0x0

 

3. I'm facing some odd memory allocation issues (only if the VM is Q35, all works well if the VM is configured as i440fx), which may req

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