[RFC v3 0/5] Introduce MMIO/PIO dispatch file descriptors (ioregionfd)

[Elena Afanasova <eafanasova@gmail.com>]

This patchset introduces a KVM dispatch mechanism which can be used 
for handling MMIO/PIO accesses over file descriptors without returning 
from ioctl(KVM_RUN). This allows device emulation to run in another task 
separate from the vCPU task.

This is achieved through KVM vm ioctl for registering MMIO/PIO regions and 
a wire protocol that KVM uses to communicate with a task handling an 
MMIO/PIO access.

TODOs:
* Implement KVM_EXIT_IOREGIONFD_FAILURE
* Add non-x86 arch support
* Add kvm-unittests
* Flush waiters if ioregion is deleted

v3:
 - add FAST_MMIO bus support
 - add KVM_IOREGION_DEASSIGN flag
 - rename kvm_ioregion read/write file descriptors
 - split ioregionfd signal handling support into two patches
 - move ioregion_interrupted flag to ioregion_ctx
 - reorder ioregion_ctx fields
 - rework complete_ioregion operations 
 - add signal handling support for crossing a page boundary case
 - change wire protocol license
 - fix ioregionfd state machine
 - remove ioregionfd_cmd info and drop appropriate macros
 - add comment on ioregionfd cmds/replies serialization
 - drop kvm_io_bus_finish/prepare()

Elena Afanasova (5):
  KVM: add initial support for KVM_SET_IOREGION
  KVM: x86: add support for ioregionfd signal handling
  KVM: implement wire protocol
  KVM: add ioregionfd context
  KVM: enforce NR_IOBUS_DEVS limit if kmemcg is disabled

 arch/x86/kvm/Kconfig          |   1 +
 arch/x86/kvm/Makefile         |   1 +
 arch/x86/kvm/vmx/vmx.c        |  40 ++-
 arch/x86/kvm/x86.c            | 273 +++++++++++++++++-
 include/linux/kvm_host.h      |  28 ++
 include/uapi/linux/ioregion.h |  30 ++
 include/uapi/linux/kvm.h      |  25 ++
 virt/kvm/Kconfig              |   3 +
 virt/kvm/eventfd.c            |  25 ++
 virt/kvm/eventfd.h            |  14 +
 virt/kvm/ioregion.c           | 529 ++++++++++++++++++++++++++++++++++
 virt/kvm/ioregion.h           |  15 +
 virt/kvm/kvm_main.c           |  36 ++-
 13 files changed, 996 insertions(+), 24 deletions(-)
 create mode 100644 include/uapi/linux/ioregion.h
 create mode 100644 virt/kvm/eventfd.h
 create mode 100644 virt/kvm/ioregion.c
 create mode 100644 virt/kvm/ioregion.h

-- 
2.25.1