From: Ravi Bangoria <ravi.bangoria@xxxxxxx> commit 54950bfe2b69cdc06ef753872b5225e54eb73506 upstream. If host supports Bus Lock Detect, KVM advertises it to guests even if SVM support is absent. Additionally, guest wouldn't be able to use it despite guest CPUID bit being set. Fix it by unconditionally clearing the feature bit in KVM cpu capability. Reported-by: Jim Mattson <jmattson@xxxxxxxxxx> Closes: https://lore.kernel.org/r/CALMp9eRet6+v8Y1Q-i6mqPm4hUow_kJNhmVHfOV8tMfuSS=tVg@xxxxxxxxxxxxxx Fixes: 76ea438b4afc ("KVM: X86: Expose bus lock debug exception to guest") Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Ravi Bangoria <ravi.bangoria@xxxxxxx> Reviewed-by: Jim Mattson <jmattson@xxxxxxxxxx> Reviewed-by: Tom Lendacky <thomas.lendacky@xxxxxxx> Link: https://lore.kernel.org/r/20240808062937.1149-4-ravi.bangoria@xxxxxxx Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/kvm/svm/svm.c | 3 +++ 1 file changed, 3 insertions(+) --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -5223,6 +5223,9 @@ static __init void svm_set_cpu_caps(void /* CPUID 0x8000001F (SME/SEV features) */ sev_set_cpu_caps(); + + /* Don't advertise Bus Lock Detect to guest if SVM support is absent */ + kvm_cpu_cap_clear(X86_FEATURE_BUS_LOCK_DETECT); } static __init int svm_hardware_setup(void) Patches currently in stable-queue which might be from ravi.bangoria@xxxxxxx are queue-6.10/kvm-svm-don-t-advertise-bus-lock-detect-to-guest-if-svm-support-is-missing.patch
