Updating QEMU machine platform on VM creates new PCI devices in windows register

[CeeJaySWE]

I've had an issue where MSI on my GTX 970 resets every time I update the QEMU machine platform (current is Q35 6.1). What I noted while working on a script for fixing the register entries was that after each update all PCI devices gets added with a new ID and settings restored. This goes for both passthrough and emulated devices. Anyone got experience of this? Is it an error on my part, UnRaid or QEMU?

[ghost82]

2 hours ago, CeeJaySWE said:

Anyone got experience of this? Is it an error on my part, UnRaid or QEMU?

qemu 6.1 machine type changed acpi tables to introduce acpi pci hotplug for q35, so what you are seeing is expected.

Personally out of my 3 vms (mac os, windows, linux) I'm using 6.1 only on linux.

Windows with q35-6.1: mellanox passed through card not working (error 10 if I remember well)

Mac os with q35-6.1: doesn't boot

 

It is also possible to use 6.1 but disabling support for the new hotplug feature, with a custom qemu arg:

<qemu:arg value="-global"/> <qemu:arg value="ICH9-LPC.acpi-pci-hotplug-with-bridge-support=off"/>

:

 

[CeeJaySWE]

1 hour ago, ghost82 said:

qemu 6.1 machine type changed acpi tables

This "issue" was present before 6.1 though so it's not the whole explanation.