EBUSY when using NVMe Block Driver with multiple devices in the same IOMMU group

[Martin Oliveira]

Hello,

I'm trying to use the QEMU NVMe userspace driver and I'm hitting an error when 
trying to use more than one device from an IOMMU group:

    Failed to open VFIO group file: /dev/vfio/39: Device or resource busy

If devices belong to different IOMMU groups, then it works as expected.

For each device, I bind it to vfio-pci and then use something like this:

    -drive file=nvme://0000:26:00.0,if=none,id=drive0,format=raw
    -device virtio-blk,drive=drive0,id=virtio0,serial=nvme0

Using the file-based protocol (file=/dev/nvme0n1) works with multiple devices 
from the same group.

My host is running a 5.19 kernel and QEMU is the latest upstream (a8cc5842b5cb).

Thanks,
Martin