[v4,00/24] KVM: x86: Event/exception fixes and cleanups

Message

Sean Christopherson July 23, 2022, 12:51 a.m. UTC

The main goal of this series is to fix KVM's longstanding bug of not
honoring L1's exception intercepts wants when handling an exception that
occurs during delivery of a different exception.  E.g. if L0 and L1 are
using shadow paging, and L2 hits a #PF, and then hits another #PF while
vectoring the first #PF due to _L1_ not having a shadow page for the IDT,
KVM needs to check L1's intercepts before morphing the #PF => #PF => #DF
so that the #PF is routed to L1, not injected into L2 as a #DF.

nVMX has hacked around the bug for years by overriding the #PF injector
for shadow paging to go straight to VM-Exit, and nSVM has started doing
the same.  The hacks mostly work, but they're incomplete, confusing, and
lead to other hacky code, e.g. bailing from the emulator because #PF
injection forced a VM-Exit and suddenly KVM is back in L1.

v4:
 - Collect reviews. [Maxim]
 - Fix a bug where an intermediate patch dropped the async #PF token
   and used a stale payload. [Maxim]
 - Tweak comments to call out that AMD CPUs generate error codes with
   bits 31:16 != 0. [Maxim]

v3:
 - https://lore.kernel.org/all/[e-mail]
 - Collect reviews. [Maxim, Jim]
 - Split a few patches into more consumable chunks. [Maxim]
 - Document that KVM doesn't correctly handle SMI+MTF (or SMI priority). [Maxim]
 - Add comment to document the instruction boundary (event window) aspect
   of block_nested_events. [Maxim]
 - Add a patch to rename inject_pending_events() and add a comment to
   document KVM's not-quite-architecturally-correct handing of instruction
   boundaries and asynchronous events. [Maxim]

v2:
  - https://lore.kernel.org/all/[e-mail]
  - Rebased to kvm/queue (commit 8baacf67c76c) + selftests CPUID
    overhaul.
    https://lore.kernel.org/all/[e-mail]
  - Treat KVM_REQ_TRIPLE_FAULT as a pending exception.

v1: https://lore.kernel.org/all/[e-mail]

Sean Christopherson (24):
  KVM: nVMX: Unconditionally purge queued/injected events on nested
    "exit"
  KVM: VMX: Drop bits 31:16 when shoving exception error code into VMCS
  KVM: x86: Don't check for code breakpoints when emulating on exception
  KVM: nVMX: Treat General Detect #DB (DR7.GD=1) as fault-like
  KVM: nVMX: Prioritize TSS T-flag #DBs over Monitor Trap Flag
  KVM: x86: Treat #DBs from the emulator as fault-like (code and
    DR7.GD=1)
  KVM: x86: Use DR7_GD macro instead of open coding check in emulator
  KVM: nVMX: Ignore SIPI that arrives in L2 when vCPU is not in WFS
  KVM: nVMX: Unconditionally clear mtf_pending on nested VM-Exit
  KVM: VMX: Inject #PF on ENCLS as "emulated" #PF
  KVM: x86: Rename kvm_x86_ops.queue_exception to inject_exception
  KVM: x86: Make kvm_queued_exception a properly named, visible struct
  KVM: x86: Formalize blocking of nested pending exceptions
  KVM: x86: Use kvm_queue_exception_e() to queue #DF
  KVM: x86: Hoist nested event checks above event injection logic
  KVM: x86: Evaluate ability to inject SMI/NMI/IRQ after potential
    VM-Exit
  KVM: nVMX: Add a helper to identify low-priority #DB traps
  KVM: nVMX: Document priority of all known events on Intel CPUs
  KVM: x86: Morph pending exceptions to pending VM-Exits at queue time
  KVM: x86: Treat pending TRIPLE_FAULT requests as pending exceptions
  KVM: VMX: Update MTF and ICEBP comments to document KVM's subtle
    behavior
  KVM: x86: Rename inject_pending_events() to
    kvm_check_and_inject_events()
  KVM: selftests: Use uapi header to get VMX and SVM exit reasons/codes
  KVM: selftests: Add an x86-only test to verify nested exception
    queueing

 arch/x86/include/asm/kvm-x86-ops.h            |   2 +-
 arch/x86/include/asm/kvm_host.h               |  35 +-
 arch/x86/kvm/emulate.c                        |   3 +-
 arch/x86/kvm/svm/nested.c                     | 110 ++---
 arch/x86/kvm/svm/svm.c                        |  20 +-
 arch/x86/kvm/vmx/nested.c                     | 331 ++++++++-----
 arch/x86/kvm/vmx/sgx.c                        |   2 +-
 arch/x86/kvm/vmx/vmx.c                        |  54 ++-
 arch/x86/kvm/x86.c                            | 450 ++++++++++++------
 arch/x86/kvm/x86.h                            |  11 +-
 tools/testing/selftests/kvm/.gitignore        |   1 +
 tools/testing/selftests/kvm/Makefile          |   1 +
 .../selftests/kvm/include/x86_64/svm_util.h   |   7 +-
 .../selftests/kvm/include/x86_64/vmx.h        |  51 +-
 .../kvm/x86_64/nested_exceptions_test.c       | 295 ++++++++++++
 15 files changed, 953 insertions(+), 420 deletions(-)
 create mode 100644 tools/testing/selftests/kvm/x86_64/nested_exceptions_test.c


base-commit: 1a4d88a361af4f2e91861d632c6a1fe87a9665c2