[vfio-users] How to hard-reset a PCI-e device?

[Taiidan at gmx.com]

Sometimes when trying to start a VM with a graphics card (nvidia of 
course) I receive these errors in dmesg and then I must restart the 
entire system to be able to assign that card again as it gets stuck in 
S3 mode.
I would like to know exactly how I can hard reset the card so that it 
can be usable again, such as killing and then restoring power to the slot.

[  144.090784] pciehp 0000:00:02.0:pcie004: Timeout on hotplug command 
0x13f1 (issued 139840 msec ago)
[  145.103321] pciehp 0000:00:02.0:pcie004: Timeout on hotplug command 
0x03f1 (issued 1012 msec ago)
[  146.135888] pciehp 0000:00:02.0:pcie004: Timeout on hotplug command 
0x03f1 (issued 2044 msec ago)
[  146.167911] vfio-pci 0000:00:13.2: enabling device (0000 -> 0002)
[  146.216069] vfio_cap_init: 0000:00:13.2 hiding cap 0xa
[  146.267953] pciehp 0000:00:0b.0:pcie004: Timeout on hotplug command 
0x13f1 (issued 139980 msec ago)
[  147.280511] pciehp 0000:00:0b.0:pcie004: Timeout on hotplug command 
0x03f1 (issued 1012 msec ago)
[  147.311080] AMD-Vi: Event logged [
[  147.311086] INVALID_DEVICE_REQUEST device=00:0c.0 
address=0x000000fdf8920000 flags=0x0a00]
[  148.313042] pciehp 0000:00:0b.0:pcie004: Timeout on hotplug command 
0x03f1 (issued 2044 msec ago)
[  148.485141] pciehp 0000:00:02.0:pcie004: Timeout on hotplug command 
0x13f1 (issued 2348 msec ago)
[  149.493675] pciehp 0000:00:02.0:pcie004: Timeout on hotplug command 
0x03f1 (issued 1008 msec ago)
[  150.554217] pciehp 0000:00:02.0:pcie004: Timeout on hotplug command 
0x03f1 (issued 2068 msec ago)
[  150.554534] vfio_bar_restore: 0000:05:00.1 reset recovery - restoring 
bars
[  150.554566] vfio_bar_restore: 0000:05:00.1 reset recovery - restoring 
bars
[  150.554696] vfio_bar_restore: 0000:05:00.0 reset recovery - restoring 
bars
[  150.554730] vfio_bar_restore: 0000:05:00.0 reset recovery - restoring 
bars
[  151.262550] vfio_bar_restore: 0000:05:00.0 reset recovery - restoring 
bars
[  151.293927] vfio_bar_restore: 0000:05:00.1 reset recovery - restoring 
bars