diff options
| author | Yosry Ahmed <yosry.ahmed@linux.dev> | 2025-11-08 00:45:19 +0000 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2025-11-09 08:49:48 +0100 |
| commit | dc55b3c3f61246e483e50c85d8d5366f9567e188 (patch) | |
| tree | 94b3d5c28d3a2bb02076c1d01e0c80584effe0f3 | |
| parent | ca00c3af8ede65d16097d322be330146d9231bd2 (diff) | |
KVM: SVM: Mark VMCB_LBR dirty when MSR_IA32_DEBUGCTLMSR is updated
The APM lists the DbgCtlMsr field as being tracked by the VMCB_LBR clean
bit. Always clear the bit when MSR_IA32_DEBUGCTLMSR is updated.
The history is complicated, it was correctly cleared for L1 before
commit 1d5a1b5860ed ("KVM: x86: nSVM: correctly virtualize LBR msrs when
L2 is running"). At that point svm_set_msr() started to rely on
svm_update_lbrv() to clear the bit, but when nested virtualization
is enabled the latter does not always clear it even if MSR_IA32_DEBUGCTLMSR
changed. Go back to clearing it directly in svm_set_msr().
Fixes: 1d5a1b5860ed ("KVM: x86: nSVM: correctly virtualize LBR msrs when L2 is running")
Reported-by: Matteo Rizzo <matteorizzo@google.com>
Reported-by: evn@google.com
Co-developed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Link: https://patch.msgid.link/20251108004524.1600006-2-yosry.ahmed@linux.dev
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
| -rw-r--r-- | arch/x86/kvm/svm/svm.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index 76055c0ba177..39538098002b 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -3004,7 +3004,11 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr) if (data & DEBUGCTL_RESERVED_BITS) return 1; + if (svm_get_lbr_vmcb(svm)->save.dbgctl == data) + break; + svm_get_lbr_vmcb(svm)->save.dbgctl = data; + vmcb_mark_dirty(svm->vmcb, VMCB_LBR); svm_update_lbrv(vcpu); break; case MSR_VM_HSAVE_PA: |