i386/cpu: Warn about why CPUID_EXT_PDCM is not available

When user requests PDCM explicitly via "+pdcm" without PMU enabled, emit
a warning to inform the user.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20250304052450.465445-3-xiaoyao.li@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 29bce67c3a1fcc6c528c759300f8afc890e9b5f3..0d35e95430fe9f8b4886a76a60aa4c92aa401d39 100644 (file)
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -8339,6 +8339,9 @@ void x86_cpu_expand_features(X86CPU *cpu, Error **errp)
     }
 
     if (!cpu->enable_pmu) {
+        mark_unavailable_features(cpu, FEAT_1_ECX,
+                                  env->user_features[FEAT_1_ECX] & CPUID_EXT_PDCM,
+                                  "This feature is not available due to PMU being disabled");
         env->features[FEAT_1_ECX] &= ~CPUID_EXT_PDCM;
     }