Manual PCI rescan required after using qvm-pci to attach PCI devices to HVMs

[qubesuser]

Qubes OS version:

R4.0-rc2

Steps to reproduce the behavior:

1. Use qvm-pci to attach a PCI devices to a running HVM VM
2. Run sudo lspci in the VM
3. Run echo 1|sudo tee /sys/bus/pci/rescan in the VM
4. Run sudo lspci in the VM

Expected behavior:

The PCI device is visible immediately after attaching with qvm-pci

Actual behavior:

The PCI device is only visible after rescanning the PCI bus in the VM.

General notes:

It looks like the Qemu machine model we are using might not support PCI hotplugging.

One option is to switch to one that does if possible (I guess q35 does?), and the other option is to just use qrexec to trigger a PCI rescan on the guest operating system.

[marmarek]

Does it work at all if VM initially had no PCI device at all?

[marmarek]

Does it work at all if VM initially had no PCI device at all?

[qubesuser]

I think it did for one device, while trying it for another device just triggered #3233 upon PCI rescan (which I now discovered is not related to using two devices apparently).

[qubesuser]

I think it did for one device, while trying it for another device just triggered #3233 upon PCI rescan (which I now discovered is not related to using two devices apparently).