qemu-kvm: iPhone USB passthrough crashes Windows 10 guest on Debian buster

On a Debian buster host running Windows 10 as a guest, running a locally compiled Linux 5.7.5 kernel, with qemu-kvm 1:3.1+dfsg-8+deb10u5:

Plugging an iPhone 6 or a first-gen iPad Pro into a USB 3 port and redirecting the device to the Windows 10 VM while it is running crashes every time.
Plugging an iPhone 6 or a first-gen iPad Pro into a USB 3 port, redirecting the device to the Windows 10 VM while it is not running, and then starting it up causes a crash on boot every time.
In both cases the crash causes an immediate power-off. Restarting the VM with the redirection in place allows the crash to be 100% reproducible. The only way to recover the VM is to remove the redirection and restart it.

No significant crash-related logs were observed in the kernel dmesg or in the plain text system logs in /var/log. A check of journalctl -xe reveals the following entry, repeated several times in line with the instant crash of the VM when the redirection is enabled:

Jun 30 10:59:26 Betelgeuse libvirtd[823]: internal error: End of file from qemu monitor

The VM has virtio version 0.1.185 installed, including the QEMU guest agent.

I found https://bugs.debian.org/cgi-bin/bugr...cgi?bug=956563 which was filed against qemu-kvm 4.2 in unstable. I'm not in a position to switch to unstable at this time on the host where this Windows 10 VM is running.

I don't see how you can fix a Windows bug by looking at the Linux logs. Event Manager on Windows should be the first place to look. Could be this:

https://discussions.apple.com/thread/7486532

Originally Posted by smallpond I don't see how you can fix a Windows bug by looking at the Linux logs. Event Manager on Windows should be the first place to look. Could be this: https://discussions.apple.com/thread/7486532

I don’t believe that this problem is in the Windows guest OS - if I had observed BSODs or other lockups I would have gone in that direction. I believe the problem is in QEMU or in the KVM client, based on the logs and behaviors I’ve observed.

I was able to solve my problem! One of the following changes eliminated the QEMU/KVM crash and allowed USB passthrough to work properly with Windows 10:

- Switching the GUI connection from VNC to Spice
- Installing the Spice Webdav agent, Spice Guest Agent and Spice QXL video drivers in the Windows 10 guest
- Configuring and activating the QEMU guest agent connection in virt-manager
- Configuring and activating the Spice Webdav connection in virt-manager

Once all of these changes were made the 100% reproducible crash went away.