[RFC v2 0/4] 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

Elena Afanasova (4):
  KVM: add initial support for KVM_SET_IOREGION
  KVM: x86: add support for ioregionfd signal handling
  KVM: add support for ioregionfd cmds/replies serialization
  KVM: enforce NR_IOBUS_DEVS limit if kmemcg is disabled

 arch/x86/kvm/Kconfig          |   1 +
 arch/x86/kvm/Makefile         |   1 +
 arch/x86/kvm/x86.c            | 216 ++++++++++++++-
 include/kvm/iodev.h           |  14 +
 include/linux/kvm_host.h      |  34 +++
 include/uapi/linux/ioregion.h |  32 +++
 include/uapi/linux/kvm.h      |  23 ++
 virt/kvm/Kconfig              |   3 +
 virt/kvm/eventfd.c            |  25 ++
 virt/kvm/eventfd.h            |  14 +
 virt/kvm/ioregion.c           | 479 ++++++++++++++++++++++++++++++++++
 virt/kvm/ioregion.h           |  15 ++
 virt/kvm/kvm_main.c           |  68 ++++-
 13 files changed, 905 insertions(+), 20 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

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2.25.1