[v4,3/4] KVM: SVM: Don't advertise Bus Lock Detect to guest if SVM support is missing

Commit Message

Ravi Bangoria Aug. 8, 2024, 6:29 a.m. UTC

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 <[e-mail]>
Closes: https://lore.kernel.org/r/CALMp9eRet6+v8Y1Q-i6mqPm4hUow_kJNhmVHfOV8tMfuSS=[e-mail]
Fixes: 76ea438b4afc ("KVM: X86: Expose bus lock debug exception to guest")
Cc: [e-mail]
Signed-off-by: Ravi Bangoria <[e-mail]>
Reviewed-by: Jim Mattson <[e-mail]>
Reviewed-by: Tom Lendacky <[e-mail]>
---
 arch/x86/kvm/svm/svm.c | 3 +++
 1 file changed, 3 insertions(+)

Patch

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index d6f252555ab3..e1b6a16e97c0 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -5224,6 +5224,9 @@  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)