Pull xen updates from Juergen Gross:

 - add dma-buf functionality to Xen grant table handling

 - fix for booting the kernel as Xen PVH dom0

 - fix for booting the kernel as a Xen PV guest with
   CONFIG_DEBUG_VIRTUAL enabled

 - other minor performance and style fixes

* tag 'for-linus-4.19-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xen/balloon: fix balloon initialization for PVH Dom0
  xen: don't use privcmd_call() from xen_mc_flush()
  xen/pv: Call get_cpu_address_sizes to set x86_virt/phys_bits
  xen/biomerge: Use true and false for boolean values
  xen/gntdev: don't dereference a null gntdev_dmabuf on allocation failure
  xen/spinlock: Don't use pvqspinlock if only 1 vCPU
  xen/gntdev: Implement dma-buf import functionality
  xen/gntdev: Implement dma-buf export functionality
  xen/gntdev: Add initial support for dma-buf UAPI
  xen/gntdev: Make private routines/structures accessible
  xen/gntdev: Allow mappings for DMA buffers
  xen/grant-table: Allow allocating buffers suitable for DMA
  xen/balloon: Share common memory reservation routines
  xen/grant-table: Make set/clear page private code shared