cherry-pick fix for KVM vCPU page fault loop

cherry-pick fix for KVM vCPU page fault loop

The mailing list thread [0] (found by Friedrich, many thanks!) leading
up to this patch sounds very familiar to issues users reported in the
community forum [1] and enterprise support channel, where a VM would
be stuck for no discernable reason with all vCPU threads spinning.

[0]: https://lore.kernel.org/all/f023d927-52aa-7e08-2ee5-59a2fbc65953@gameservers.com/T/#u
[1]: https://forum.proxmox.com/threads/127459/

Suggested-by: Friedrich Weber <f.weber@proxmox.com>
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>