[PATCH 5/8] KVM: selftests: Skip PERF_CAPABILITIES vCPU checks without PDCM

[Ewan Hai-oc]

From: Frank Zhu <frankzhu@xxxxxxxxxxx>

KVM allows userspace to query MSR_IA32_PERF_CAPABILITIES through
KVM_GET_MSRS even when PDCM is not exposed in KVM_GET_SUPPORTED_CPUID.
However, vCPU accesses to the MSR fail without PDCM.

Keep the feature MSR query, but skip its checks when KVM does not
expose PDCM, allowing feature_msrs_test to continue checking the
remaining feature MSRs.

Signed-off-by: Frank Zhu <frankzhu@xxxxxxxxxxx>
Signed-off-by: Ewan Hai <ewanhai-oc@xxxxxxxxxxx>
---
 tools/testing/selftests/kvm/x86/feature_msrs_test.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/tools/testing/selftests/kvm/x86/feature_msrs_test.c b/tools/testing/selftests/kvm/x86/feature_msrs_test.c
index 158550701771..9602e29bf9cc 100644
--- a/tools/testing/selftests/kvm/x86/feature_msrs_test.c
+++ b/tools/testing/selftests/kvm/x86/feature_msrs_test.c
@@ -54,6 +54,19 @@ static void test_feature_msr(u32 msr)
 	if (is_kvm_controlled_msr(msr))
 		return;
 
+	/*
+	 * KVM allows userspace to query MSR_IA32_PERF_CAPABILITIES as a
+	 * feature MSR even if KVM doesn't expose PDCM, but vCPU accesses to
+	 * the MSR will fail in that case. Skip the vCPU checks so that the
+	 * remaining feature MSRs can be tested.
+	 */
+	if (msr == MSR_IA32_PERF_CAPABILITIES &&
+	    !kvm_cpu_has(X86_FEATURE_PDCM)) {
+		printf("KVM does not expose PDCM, skipping vCPU checks for "
+		       "MSR_IA32_PERF_CAPABILITIES (0x%x).\n", msr);
+		return;
+	}
+
 	/*
 	 * More goofy behavior.  KVM reports the host CPU's actual revision ID,
 	 * but initializes the vCPU's revision ID to an arbitrary value.
-- 
2.34.1