November 7, 2025 at 4:45 PM, "Yosry Ahmed" <yosry.ahmed@linux.dev mailto:yosry.ahmed@linux.dev?to=%22Yosry%20Ahmed%22%20%3Cyosry.ahmed%40linux.dev%3E > wrote:
MSR_IA32_DEBUGCTLMSR and LBR MSRs are currently not enumerated by KVM_GET_MSR_INDEX_LIST, and LBR MSRs cannot be set with KVM_SET_MSRS. So save/restore is completely broken.
Fix it by adding the MSRs to msrs_to_save_base, and allowing writes to LBR MSRs from userspace only (as they are read-only MSRs). Additionally, to correctly restore L1's LBRs while L2 is running, make sure the LBRs are copied from the captured VMCB01 save area in svm_copy_vmrun_state().
Fixes: 24e09cbf480a ("KVM: SVM: enable LBR virtualization") Cc: stable@vger.kernel.org
Reported-by: Jim Mattson jmattson@google.com
Signed-off-by: Yosry Ahmed yosry.ahmed@linux.dev
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