The patches for XSA-343 produced some fallout, especially the event
channel locking has shown to be problematic.

Patch 1 is targeting fifo event channels for avoiding any races for the
case that the fifo queue has been changed for a specific event channel.

The second patch is modifying the per event channel locking scheme in
order to avoid deadlocks and problems due to the event channel lock
having been changed to require IRQs off by the XSA-343 patches.

Changes in V3:
- addressed comments

Juergen Gross (2):
  xen/events: access last_priority and last_vcpu_id together
  xen/evtchn: rework per event channel lock

 xen/arch/x86/irq.c         |   6 +-
 xen/arch/x86/pv/shim.c     |   9 +--
 xen/common/event_channel.c | 109 +++++++++++++++++--------------------
 xen/common/event_fifo.c    |  25 +++++++--
 xen/include/xen/event.h    |  76 ++++++++++++++++++++++----
 xen/include/xen/sched.h    |   5 +-
 6 files changed, 145 insertions(+), 85 deletions(-)

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2.26.2