Description:

We can add 50 virtio-blk disks into one CNV VM successfully, but according to the  bz#2219553#c3,  it should be limited to about 28 disks when we use virtio-blk. 

Test Steps:

1. Create a CNV VM with 50 disks that is virtio-blk driver. 
2. Running the VM successfully
3. Login the VM successfully 
4. Run the $ lsblk to check the block device. 

Test Result:  there are 50 disks(virtio-blk) are attached into one CNV VM.

Expected Results:

According to the bug bz#2219553#c3, the max disk with virtio-blk should be about 28.

And checking the qemu doc, it should have return error as the following if more than 28 virtio-blk disks attached to VM:

error: Failed to attach disk
error: internal error: No more available PCI slots

 

$ lsblk  | grep -c disk
52

Adding PVC :
oc patch vm rhel9-server -n default --type='json' -p='[{'op': 'add', 'path': '/spec/template/spec/volumes/-', 'value': {'name': 'pvc-test-1', 'persistentVolumeClaim': {'claimName': 'pvc-test-1'}}}]'
virtualmachine.kubevirt.io/rhel9-server patched
oc patch vm rhel9-server -n default --type='json' -p='[{'op': 'add', 'path': '/spec/template/spec/volumes/-', 'value': {'name': 'pvc-test-2', 'persistentVolumeClaim': {'claimName': 'pvc-test-2'}}}]'
virtualmachine.kubevirt.io/rhel9-server patched
oc patch vm rhel9-server -n default --type='json' -p='[{'op': 'add', 'path': '/spec/template/spec/volumes/-', 'value': {'name': 'pvc-test-3', 'persistentVolumeClaim': {'claimName': 'pvc-test-3'}}}]'
virtualmachine.kubevirt.io/rhel9-server patched

Setting interface to virtio:
oc patch vm rhel9-server -n default --type='json' -p='[{'op': 'add', 'path': '/spec/template/spec/domain/devices/disks/-', 'value': {'name': 'pvc-test-1', 'disk': {'bus': 'virtio'}}}]'
virtualmachine.kubevirt.io/rhel9-server patched
oc patch vm rhel9-server -n default --type='json' -p='[{'op': 'add', 'path': '/spec/template/spec/domain/devices/disks/-', 'value': {'name': 'pvc-test-2', 'disk': {'bus': 'virtio'}}}]'
virtualmachine.kubevirt.io/rhel9-server patched
oc patch vm rhel9-server -n default --type='json' -p='[{'op': 'add', 'path': '/spec/template/spec/domain/devices/disks/-', 'value': {'name': 'pvc-test-3', 'disk': {'bus': 'virtio'}}}]'
virtualmachine.kubevirt.io/rhel9-server patched
  

Additional information:

The bare metal node has 7 PCI slots.

I have also checked the virtio-blk device list at the OS :

$lsblk -d -o name,type,subsystems | grep -c "block:virtio:pci"
52

When i have added 100 virtio-blk disks, it was added successfully but when I have started the OS I saw only 93 disks at the lsblk.