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redhat: stop tainting the kernel with virtio-mem

David Hildenbrand requested to merge davidhildenbrand/centos-stream-9:virtio-mem-no-taint into main

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2228379

Upstream Status: RHEL only

Tested: Attached a virtio-mem device to a RHEL9 VM and made sure that the driver is loaded and the kernel is not tainted. Further, made sure that the "bbm_safe_unplug" parameter no longer shows up under /sys/module/virtio_mem/parameters/.

Let's stop tainting the kernel simply because a virtio-mem device is attached and the driver is loaded.

From a kernel / memory hot(un)plug point of view, virtio-mem works nowadays at least as good as DIMM-based memory hot(un)plug.

That virtio-mem is active can be observed, for example, using dmesg:

  [root@vm-0 ~]# dmesg | grep virtio_mem
  [    3.286652] virtio_mem virtio0: start address: 0x180000000
  [    3.290898] virtio_mem virtio0: region size: 0x800000000
  [    3.294758] virtio_mem virtio0: device block size: 0x200000
  [    3.298746] virtio_mem virtio0: nid: 0
  [    3.301568] virtio_mem virtio0: memory block size: 0x8000000
  [    3.305360] virtio_mem virtio0: subblock size: 0x400000
  [    3.309225] virtio_mem virtio0: plugged size: 0x0
  [    3.312397] virtio_mem virtio0: requested size: 0x3e800000

Or /proc/iomem:

  [root@vm-0 ~]# cat /proc/iomem
  ...
  180000000-97fffffff : virtio0
    180000000-1bfffffff : System RAM (virtio_mem)
  ...

Further, whenever the hypervisor requests a size change (such that virtio-mem would go ahead and try (un)plugging memory), we get additional info in dmesg such that we could correlate events:

  [  159.583623] virtio_mem virtio0: plugged size: 0x3e800000
  [  159.587320] virtio_mem virtio0: requested size: 0x4000000

As we stop tainting the kernel, hide the "bbm_safe_unplug" kernel parameter in RHEL 9, because we really don't want that to ever be active.

Signed-off-by: David Hildenbrand david@redhat.com

Edited by David Hildenbrand

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