Commits on May 18, 2022

1. core: Add memtune hard_limit for q35 VMs with many CPUs …

   When a VM with q35 chipset has at least 256 maximum vCPUs and contains
   VFIO devices, it can fail to start.  It can happen for two reasons:
   
   1. There are multiple VFIO devices in the same IOMMU group and their
      drivers don’t handle it properly.
   
   2. The memory locking limit needed to handle the VFIO devices is
      exceeded.
   
   oVirt cannot do anything about 1., such a situation must be fixed in
   the low level layers.  As for 2., it should be fixed in QEMU one day
   but we can work around it now by specifying a sufficiently high limit
   on the amount of QEMU and guest memory locked in the host
   memory (i.e. not being able to swap out).  The limit should be at
   least VM maximum RAM times the number of VFIO devices.  We set it
   simply to an extremely high value regardless the presence and number
   of VFIO devices, which should cause no trouble because we don’t want
   to swap out VM memory anyway.
   
   See https://bugzilla.redhat.com/show_bug.cgi?id=2048429#c9 for more
   details.
   
   Bug-Url: https://bugzilla.redhat.com/2081241
   Bug-Url: https://bugzilla.redhat.com/2048429

   

   mz-pdm committed May 18, 2022
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