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

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Message-ID: <20251108004524.1600006-1-yosry.ahmed@linux.dev>
Date: Sat,  8 Nov 2025 00:45:18 +0000
From: Yosry Ahmed <yosry.ahmed@...ux.dev>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>,
	Jim Mattson <jmattson@...gle.com>,
	Maxim Levitsky <mlevitsk@...hat.com>,
	kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Yosry Ahmed <yosry.ahmed@...ux.dev>
Subject: [PATCH 0/6] KVM: SVM: LBR virtualization fixes

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

-- 
2.51.2.1041.gc1ab5b90ca-goog