xen: various flaws (#1463247)
      blkif responses leak backend stack data [XSA-216]
      page transfer may allow PV guest to elevate privilege [XSA-217]
      Races in the grant table unmap code [XSA-218]
      x86: insufficient reference counts during shadow emulation [XSA-219]
      x86: PKRU and BND* leakage between vCPU-s [XSA-220]
      NULL pointer deref in event channel poll [XSA-221]
      stale P2M mappings due to insufficient error checking [XSA-222]
      ARM guest disabling interrupt may crash Xen [XSA-223]
      grant table operations mishandle reference counts [XSA-224]
      arm: vgic: Out-of-bound access when sending SGIs [XSA-225]