[vfio-users] vm lags/pauses when IO overloaded on host

[Jiri 'Ghormoon' Novak]

Hi,

for quite long time, I've got an issue with my drives configuration on
my VMs that do vga passthrough (but I think it's unrelated to
passthrough as they would lag without passthrough too).
the config is

-drive
file=/dev/something,if=none,id=drive-virtio-disk0,format=raw,cache=none,aio=native
-device
virtio-blk-pci,scsi=off,bus=pci.2,addr=0x1,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1

what parameter am I missing so the guest would be waiting for IO and not
the host pausing it until it can provide the IO?

for some time I thought it was windows problem ,but it also shows on my
linux guest when the IO lacks.

if it matters, the backend is zfs zvol. that's why especially on HDDs it
hurts a lot. on SSD it's not that bad but still if I load the IO a lot
from multiple sources, it has problem.

Thanks,
Ghor