Hi, I recently tried to pass through a USB flash drive to a VM using QEMU, and I couldn't get it working. Has anyone successfully used QEMU's USB pass-through feature on a Guix system? When I plug a USB flash drive into my Guix system using GNOME, GNOME automatically mounts it for me. So I unmounted by running "umount" as root. It didn't seem to get automatically re-mounted, which is good, and by running "lsblk -f" I verified that it remained unmounted. Based on the output of "lsusb", this flash drive uses bus address 001, and device address 006. I tried launching the VM like this: qemu-system-x86_64 \ -net user,hostfwd=tcp:127.0.0.1:2222-:22 \ -net nic,model=virtio \ -enable-kvm \ -m 512 \ -smp 1 \ -device virtio-blk,drive=myhd \ -drive if=none,file=debian,id=myhd \ -vga std \ -usb \ -device usb-host,hostbus=1,hostaddr=8 \ -monitor stdio Note that for QEMU to launch without errors, I had to give myself read/write permissions on the USB device node: $ sudo setfacl -m u:marusich:rw /dev/bus/usb/001/008 QEMU launches the VM launches without errors. Within it, I can see a block device at /dev/sda (the virtual hard drive "myhd" shows up as /dev/vda). However, when I try to read from it, it doesn't work: marusich@debian:~$ sudo head --bytes=512 /dev/sda | hexdump -C [sudo] password for marusich: head: error reading '/dev/sda': Input/output error Meanwhile, in the host, dmesg says stuff like this. First, right after I launch the VM: [169152.893485] udevd[215]: specified group 'plugdev' unknown [169152.973558] sd 4:0:0:0: [sdb] Synchronizing SCSI cache [169153.306104] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169155.074112] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169155.374116] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169167.054727] kvm [22097]: vcpu0, guest rIP: 0xffffffff9565db48 disabled perfctr wrmsr: 0xc2 data 0xffff [169167.265174] udevd[215]: specified group 'plugdev' unknown [169167.394116] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169170.006107] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169170.605105] udevd[215]: specified group 'plugdev' unknown [169170.718133] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169171.146116] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169176.759220] udevd[215]: specified group 'plugdev' unknown [169176.870112] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169178.838435] udevd[215]: specified group 'plugdev' unknown [169178.966118] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169180.438119] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169181.650113] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169183.564845] udevd[215]: specified group 'plugdev' unknown [169184.066115] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169185.446110] usb 1-1: reset high-speed USB device number 9 using ehci-pci Even after I shut down the VM, the messages continue: [169186.776158] udevd[215]: specified group 'plugdev' unknown [169186.894128] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169187.594122] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169188.442126] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169189.194114] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169189.933640] udevd[215]: specified group 'plugdev' unknown [169190.058150] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169190.746120] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169191.566121] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169192.290112] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169193.158971] udevd[215]: specified group 'plugdev' unknown [169193.282121] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169193.706136] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169194.530116] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169194.954115] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169195.774120] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169196.194117] usb 1-1: reset high-speed USB device number 9 using ehci-pci But eventually, the USB device stops getting reset, and it shows up automatically in my host system again (GNOME proceeds to auto-mount it, too): [169324.539442] udevd[215]: specified group 'plugdev' unknown [169324.654115] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169325.086114] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169325.898113] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169326.326106] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169327.142098] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169327.574131] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169327.754133] udevd[215]: specified group 'plugdev' unknown [169328.126102] usb 1-1: reset high-speed USB device number 9 using ehci-pci [169328.466887] usb-storage 1-1:1.0: USB Mass Storage device detected [169328.485130] scsi host4: usb-storage 1-1:1.0 [169329.846284] scsi 4:0:0:0: Direct-Access SMI USB DISK 1100 PQ: 0 ANSI: 6 [169329.847241] sd 4:0:0:0: Attached scsi generic sg1 type 0 [169329.848630] sd 4:0:0:0: [sdb] 61440000 512-byte logical blocks: (31.5 GB/29.3 GiB) [169329.852458] sd 4:0:0:0: [sdb] Write Protect is off [169329.852460] sd 4:0:0:0: [sdb] Mode Sense: 43 00 00 00 [169329.853665] sd 4:0:0:0: [sdb] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA [169329.860891] sdb: sdb1 sdb2 [169329.865264] sd 4:0:0:0: [sdb] Attached SCSI removable disk This is pretty weird. I tried all of the following, but I saw the same results every time: * Run QEMU as root. * Unbind the ehci-pci driver (so Linux will use uhci_hcd instead) * Pass additional -device options for the other USB devices, including a hub that shows up on the same bus. * Try a different USB port. * Try a different USB storage device. If anyone has gotten USB pass-through working with QEMU on a Guix system, please let me know what I'm doing wrong! Thank you, -- Chris