[PATCH V6 0/6] Fast mmio eventfd fixes

[Jason Wang]

Hi:

This series fixes two issues of fast mmio eventfd:

1) A single iodev instance were registerd on two buses: KVM_MMIO_BUS
   and KVM_FAST_MMIO_BUS. This will cause double in
   ioeventfd_destructor()
2) A zero length iodev on KVM_MMIO_BUS will never be found but
   kvm_io_bus_cmp(). This will lead e.g the eventfd will be trapped by
   qemu instead of host.

1 is fixed by allocating two instances of iodev and introduce a new
capability for userspace. 2 is fixed by ignore the actual length if
the length of iodev is zero in kvm_io_bus_cmp().

Please review.

Changes from V5:
- move patch of explicitly checking for KVM_MMIO_BUS to patch 1 and
  remove the unnecessary checks
- even more grammar and typo fixes
- rabase to kvm.git
- document KVM_CAP_FAST_MMIO

Changes from V4:
- move the location of kvm_assign_ioeventfd() in patch 1 which reduce
  the change set.
- commit log typo fixes
- switch to use kvm_deassign_ioeventfd_id) when fail to register to
  fast mmio bus
- change kvm_io_bus_cmp() as Paolo's suggestions
- introduce a new capability to avoid new userspace crash old kernel
- add a new patch that only try to register mmio eventfd on fast mmio
  bus

Changes from V3:

- Don't do search on two buses when trying to do write on
  KVM_MMIO_BUS. This fixes a small regression found by vmexit.flat.
- Since we don't do search on two buses, change kvm_io_bus_cmp() to
  let it can find zero length iodevs.
- Fix the unnecessary lines in tracepoint patch.

Changes from V2:
- Tweak styles and comment suggested by Cornelia.

Changes from v1:
- change ioeventfd_bus_from_flags() to return KVM_FAST_MMIO_BUS when
  needed to save lots of unnecessary changes.

Jason Wang (6):
  kvm: don't try to register to KVM_FAST_MMIO_BUS for non mmio eventfd
  kvm: factor out core eventfd assign/deassign logic
  kvm: fix double free for fast mmio eventfd
  kvm: fix zero length mmio searching
  kvm: add tracepoint for fast mmio
  kvm: add fast mmio capabilitiy

 Documentation/virtual/kvm/api.txt |   7 ++-
 arch/x86/kvm/trace.h              |  18 ++++++
 arch/x86/kvm/vmx.c                |   1 +
 arch/x86/kvm/x86.c                |   1 +
 include/uapi/linux/kvm.h          |   1 +
 virt/kvm/eventfd.c                | 124 ++++++++++++++++++++++----------------
 virt/kvm/kvm_main.c               |  20 +++++-
 7 files changed, 118 insertions(+), 54 deletions(-)

-- 
2.1.4

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