KVM: x86: Print names of apicv inhibit reasons in traces

Use the tracing infrastructure helper __print_flags() for printing flag
bitfields, to enhance the trace output by displaying a string describing
each of the inhibit reasons set.

The kvm_apicv_inhibit_changed tracepoint currently shows the raw bitmap
value, requiring the user to consult the source file where the inhibit
reasons are defined to decode the trace output.
Signed-off-by: Alejandro Jimenez <alejandro.j.jimenez@oracle.com>
Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
Link: https://lore.kernel.org/r/20240506225321.3440701-2-alejandro.j.jimenez@oracle.comCo-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>

arch/x86/include/asm/kvm_host.h

@@ -1277,8 +1277,27 @@ enum kvm_apicv_inhibit {
 	 * mapping between logical ID and vCPU.
 	 */
 	APICV_INHIBIT_REASON_LOGICAL_ID_ALIASED,
+
+	NR_APICV_INHIBIT_REASONS,
 };
 
+#define __APICV_INHIBIT_REASON(reason)			\
+	{ BIT(APICV_INHIBIT_REASON_##reason), #reason }
+
+#define APICV_INHIBIT_REASONS				\
+	__APICV_INHIBIT_REASON(DISABLE),		\
+	__APICV_INHIBIT_REASON(HYPERV),			\
+	__APICV_INHIBIT_REASON(ABSENT),			\
+	__APICV_INHIBIT_REASON(BLOCKIRQ),		\
+	__APICV_INHIBIT_REASON(PHYSICAL_ID_ALIASED),	\
+	__APICV_INHIBIT_REASON(APIC_ID_MODIFIED),	\
+	__APICV_INHIBIT_REASON(APIC_BASE_MODIFIED),	\
+	__APICV_INHIBIT_REASON(NESTED),			\
+	__APICV_INHIBIT_REASON(IRQWIN),			\
+	__APICV_INHIBIT_REASON(PIT_REINJ),		\
+	__APICV_INHIBIT_REASON(SEV),			\
+	__APICV_INHIBIT_REASON(LOGICAL_ID_ALIASED)
+
 struct kvm_arch {
 	unsigned long n_used_mmu_pages;
 	unsigned long n_requested_mmu_pages;

arch/x86/kvm/trace.h

@@ -1375,6 +1375,10 @@ TRACE_EVENT(kvm_hv_stimer_cleanup,
 		  __entry->vcpu_id, __entry->timer_index)
 );
 
+#define kvm_print_apicv_inhibit_reasons(inhibits)	\
+	(inhibits), (inhibits) ? " " : "",		\
+	(inhibits) ? __print_flags(inhibits, "|", APICV_INHIBIT_REASONS) : ""
+
 TRACE_EVENT(kvm_apicv_inhibit_changed,
 	    TP_PROTO(int reason, bool set, unsigned long inhibits),
 	    TP_ARGS(reason, set, inhibits),
@@ -1391,9 +1395,10 @@ TRACE_EVENT(kvm_apicv_inhibit_changed,
 		__entry->inhibits = inhibits;
 	),
 
-	TP_printk("%s reason=%u, inhibits=0x%lx",
+	TP_printk("%s reason=%u, inhibits=0x%lx%s%s",
 		  __entry->set ? "set" : "cleared",
-		  __entry->reason, __entry->inhibits)
+		  __entry->reason,
+		  kvm_print_apicv_inhibit_reasons(__entry->inhibits))
 );
 
 TRACE_EVENT(kvm_apicv_accept_irq,

arch/x86/kvm/x86.c

@@ -10037,6 +10037,10 @@ EXPORT_SYMBOL_GPL(kvm_vcpu_apicv_activated);
 static void set_or_clear_apicv_inhibit(unsigned long *inhibits,
 				       enum kvm_apicv_inhibit reason, bool set)
 {
+	const struct trace_print_flags apicv_inhibits[] = { APICV_INHIBIT_REASONS };
+
+	BUILD_BUG_ON(ARRAY_SIZE(apicv_inhibits) != NR_APICV_INHIBIT_REASONS);
+
 	if (set)
 		__set_bit(reason, inhibits);
 	else