[PATCH 0/6] KVM: SVM: LBR virtualization fixes

Yosry Ahmed
2025-11-08T00:45:51Z

This series fixes multiple problems with LBR virtualization, including a
fun problem that leads to L1 reading the host's LBR MSRs. It also
considerably simplifies the code.

The series has a selftest in the end that verifies that save/restore
work correctly. I will send a couple of new kvm-unit-tests separately
that exercise the bugs fixed by patches 2 & 3.

Yosry Ahmed (6):
KVM: SVM: Mark VMCB_LBR dirty when MSR_IA32_DEBUGCTLMSR is updated
KVM: nSVM: Always recalculate LBR MSR intercepts in svm_update_lbrv()
KVM: nSVM: Fix and simplify LBR virtualization handling with nested
KVM: SVM: Switch svm_copy_lbrs() to a macro
KVM: SVM: Add missing save/restore handling of LBR MSRs
KVM: selftests: Add a test for LBR save/restore (ft. nested)

arch/x86/kvm/svm/nested.c | 31 ++--
arch/x86/kvm/svm/svm.c | 98 ++++++-----
arch/x86/kvm/svm/svm.h | 10 +-
arch/x86/kvm/x86.c | 3 +
tools/testing/selftests/kvm/Makefile.kvm | 1 +
.../selftests/kvm/include/x86/processor.h | 5 +
.../selftests/kvm/x86/svm_lbr_nested_state.c | 155 ++++++++++++++++++
7 files changed, 236 insertions(+), 67 deletions(-)
create mode 100644 tools/testing/selftests/kvm/x86/svm_lbr_nested_state.c

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2.51.2.1041.gc1ab5b90ca-goog