[RFC 0/2] 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.

ioregionfd relies on kmemcg in order to limit the amount of kernel memory 
that userspace can consume. Can NR_IOBUS_DEVS hardcoded limit be enforced 
only in case kmemcg is disabled?

Elena Afanasova (2):
  KVM: add initial support for KVM_SET_IOREGION
  KVM: add initial support for ioregionfd blocking read/write operations

 arch/x86/kvm/Kconfig     |   1 +
 arch/x86/kvm/Makefile    |   1 +
 arch/x86/kvm/x86.c       |   1 +
 include/linux/kvm_host.h |  17 ++
 include/uapi/linux/kvm.h |  23 +++
 virt/kvm/Kconfig         |   3 +
 virt/kvm/eventfd.c       |  25 +++
 virt/kvm/eventfd.h       |  14 ++
 virt/kvm/ioregion.c      | 390 +++++++++++++++++++++++++++++++++++++++
 virt/kvm/ioregion.h      |  15 ++
 virt/kvm/kvm_main.c      |  20 +-
 11 files changed, 507 insertions(+), 3 deletions(-)
 create mode 100644 virt/kvm/eventfd.h
 create mode 100644 virt/kvm/ioregion.c
 create mode 100644 virt/kvm/ioregion.h

-- 
2.25.1