irqfd enhancements, and irq_routing fixes

(Applies to kvm.git/master:11b06403)

The following patches are cleanups/enhancements for IRQFD now that we have lockless interrupt injection. For more details, please see the patch headers.

These patches pass checkpatch, and are fully tested. Please consider for merging. Patch 1/3 is a fix for an issue that may exist upstream and should be considered for a more timely push upstream. Patches 2/3
- 3/3 are an enhancement only, so there is no urgency to push to mainline until a suitable merge window presents itself.

Kind Regards,
-Greg

[ Change log:

v3:
*) Added patch 1/3 as a fix for a race condition
*) Minor cleanup to 2/3 to ensure that all shared vectors conform
to a unified locking model.

v2:
*) dropped original cleanup which relied on the user registering
MSI based GSIs or we may crash at runtime. Instead, we now check at registration whether the GSI supports lockless operation and dynamically adapt to either the original deferred path for lock-based injections, or direct for lockless.

v1:
*) original release
]

---

Gregory Haskins (3):
KVM: Directly inject interrupts if they support lockless operation
KVM: export lockless GSI attribute
KVM: fix race in irq_routing logic

 include/linux/kvm_host.h |    8 ++++
 virt/kvm/eventfd.c       |   31 +++++++++++++++--
 virt/kvm/irq_comm.c      |   85 ++++++++++++++++++++++++++++++++++------------
 virt/kvm/kvm_main.c      |    1 +
 4 files changed, 98 insertions(+), 27 deletions(-)

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