Pull xen updates from Juergen Gross:
 "Xen features and fixes:

   - a series to enable KVM guests to be booted by qemu via the Xen PVH
     boot entry for speeding up KVM guest tests

   - a series for a common driver to be used by Xen PV frontends (right
     now drm and sound)

   - two other fixes in Xen related code"

* tag 'for-linus-4.21-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  ALSA: xen-front: Use Xen common shared buffer implementation
  drm/xen-front: Use Xen common shared buffer implementation
  xen: Introduce shared buffer helpers for page directory...
  xen/pciback: Check dev_data before using it
  kprobes/x86/xen: blacklist non-attachable xen interrupt functions
  KVM: x86: Allow Qemu/KVM to use PVH entry point
  xen/pvh: Add memory map pointer to hvm_start_info struct
  xen/pvh: Move Xen code for getting mem map via hcall out of common file
  xen/pvh: Move Xen specific PVH VM initialization out of common file
  xen/pvh: Create a new file for Xen specific PVH code
  xen/pvh: Move PVH entry code out of Xen specific tree
  xen/pvh: Split CONFIG_XEN_PVH into CONFIG_PVH and CONFIG_XEN_PVH