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.
Everything leading up to that are related fixes and cleanups I encountered
along the way; some through code inspection, some through tests.
v2:
- Rebased to kvm/queue (commit 8baacf67c76c) + selftests CPUID
overhaul.
https://lore.kernel.org/all/20220614200707.3315957-1-seanjc@xxxxxxxxxx
- Treat KVM_REQ_TRIPLE_FAULT as a pending exception.
v1: https://lore.kernel.org/all/20220311032801.3467418-1-seanjc@xxxxxxxxxx
Sean Christopherson (21):
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: 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: 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 | 102 ++---
arch/x86/kvm/svm/svm.c | 18 +-
arch/x86/kvm/vmx/nested.c | 319 +++++++++-----
arch/x86/kvm/vmx/sgx.c | 2 +-
arch/x86/kvm/vmx/vmx.c | 53 ++-
arch/x86/kvm/x86.c | 404 +++++++++++-------
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, 886 insertions(+), 418 deletions(-)
create mode 100644 tools/testing/selftests/kvm/x86_64/nested_exceptions_test.c
base-commit: 816967202161955f398ce379f9cbbedcb1eb03cb
--
2.36.1.476.g0c4daa206d-goog
