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Subject[PATCH v2 00/24] KVM: x86: Event/exception fixes and cleanups
From
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.

Maxim, I believe I addressed all of your comments, holler if I missed
something.

v2:
- 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]

v1: https://lore.kernel.org/all/20220614204730.3359543-1-seanjc@google.com

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 | 329 ++++++++-----
arch/x86/kvm/vmx/sgx.c | 2 +-
arch/x86/kvm/vmx/vmx.c | 53 ++-
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, 950 insertions(+), 420 deletions(-)
create mode 100644 tools/testing/selftests/kvm/x86_64/nested_exceptions_test.c


base-commit: 8031d87aa9953ddeb047a5356ebd0b240c30f233
--
2.37.0.170.g444d1eabd0-goog

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