[PATCH v6 0/3] Introduce Notify VM exit

[Chenyi Qiang <chenyi.qiang@intel.com>]

Virtual machines can exploit Intel ISA characterstics to cause
functional denial of service to the VMM. This series introduces a new
feature named Notify VM exit, which can help mitigate such kind of
attacks.

Patch 1: An extension of KVM_SET_VCPU_EVENTS ioctl to inject a
synthesized shutdown event from user space. This is also a fix for other
synthesized triple fault, e.g. the RSM patch or nested_vmx_abort(),
which could get lost when exit to userspace to do migrate.

Patch 2: A selftest about get/set triple fault event.

Patch 3: The main patch to enable Notify VM exit.

---
Change logs:
v5 -> v6
- Do some changes in document.
- Add a selftest about get/set triple fault event. (Sean)
- extend the argument to include both the notify window and some flags
  when enabling KVM_CAP_X86_BUS_LOCK_EXIT CAP. (Sean)
- Change to use KVM_VCPUEVENT_VALID_TRIPE_FAULT in flags field and add
  pending_triple_fault field in struct kvm_vcpu_events, which allows
  userspace to make/clear triple fault request. (Sean)
- Add a flag in kvm_x86_ops to avoid the kvm_has_notify_vmexit global
  varialbe and its export.(Sean)
- v5: https://lore.kernel.org/lkml/20220318074955.22428-1-chenyi.qiang@intel.com/

v4 -> v5
- rename KVM_VCPUEVENTS_SHUTDOWN to KVM_VCPUEVENTS_TRIPLE_FAULT. Make it
  bidirection and add it to get_vcpu_events. (Sean)
- v4: https://lore.kernel.org/all/20220310084001.10235-1-chenyi.qiang@intel.com/

v3 -> v4
- Change this feature to per-VM scope. (Jim)
- Once VM_CONTEXT_INVALID set in exit_qualification, exit to user space
  notify this fatal case, especially the notify VM exit happens in L2.
  (Jim)
- extend KVM_SET_VCPU_EVENTS to allow user space to inject a shutdown
  event. (Jim)
- A minor code changes.
- Add document for the new KVM capability.
- v3: https://lore.kernel.org/lkml/20220223062412.22334-1-chenyi.qiang@intel.com/

v2 -> v3
- add a vcpu state notify_window_exits to record the number of
  occurence as well as a pr_warn output. (Sean)
- Add the handling in nested VM to prevent L1 bypassing the restriction
  through launching a L2. (Sean)
- Only kill L2 when L2 VM is context invalid, synthesize a
  EXIT_REASON_TRIPLE_FAULT to L1 (Sean)
- To ease the current implementation, make module parameter
  notify_window read-only. (Sean)
- Disable notify window exit by default.
- v2: https://lore.kernel.org/lkml/20210525051204.1480610-1-tao3.xu@intel.com/

v1 -> v2
- Default set notify window to 0, less than 0 to disable.
- Add more description in commit message.
---

Chenyi Qiang (2):
  KVM: X86: Save&restore the triple fault request
  KVM: selftests: Add a test to get/set triple fault event

Tao Xu (1):
  KVM: VMX: Enable Notify VM exit

 Documentation/virt/kvm/api.rst                | 55 +++++++++++
 arch/x86/include/asm/kvm_host.h               |  9 ++
 arch/x86/include/asm/vmx.h                    |  7 ++
 arch/x86/include/asm/vmxfeatures.h            |  1 +
 arch/x86/include/uapi/asm/kvm.h               |  4 +-
 arch/x86/include/uapi/asm/vmx.h               |  4 +-
 arch/x86/kvm/vmx/capabilities.h               |  6 ++
 arch/x86/kvm/vmx/nested.c                     |  8 ++
 arch/x86/kvm/vmx/vmx.c                        | 48 +++++++++-
 arch/x86/kvm/x86.c                            | 33 ++++++-
 arch/x86/kvm/x86.h                            |  5 +
 include/uapi/linux/kvm.h                      | 10 ++
 tools/testing/selftests/kvm/.gitignore        |  1 +
 tools/testing/selftests/kvm/Makefile          |  1 +
 .../kvm/x86_64/triple_fault_event_test.c      | 96 +++++++++++++++++++
 15 files changed, 280 insertions(+), 8 deletions(-)
 create mode 100644 tools/testing/selftests/kvm/x86_64/triple_fault_event_test.c

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2.17.1