3 files changed, 69 insertions, 2 deletions

diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index e8ddb128b8ad..1fc6fef463db 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -76,6 +76,19 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
 	{NULL}
 };
 
+bool kvm_trace_guest_mode_change;
+
+int kvm_guest_mode_change_trace_reg(void)
+{
+	kvm_trace_guest_mode_change = 1;
+	return 0;
+}
+
+void kvm_guest_mode_change_trace_unreg(void)
+{
+	kvm_trace_guest_mode_change = 0;
+}
+
 /*
  * XXXKYMA: We are simulatoring a processor that has the WII bit set in
  * Config7, so we are "runnable" if interrupts are pending
diff --git a/arch/mips/kvm/trace.h b/arch/mips/kvm/trace.h
index affde8a2c584..a8c7fd7bf6d2 100644
--- a/arch/mips/kvm/trace.h
+++ b/arch/mips/kvm/trace.h
@@ -18,6 +18,13 @@
 #define TRACE_INCLUDE_FILE trace
 
 /*
+ * arch/mips/kvm/mips.c
+ */
+extern bool kvm_trace_guest_mode_change;
+int kvm_guest_mode_change_trace_reg(void);
+void kvm_guest_mode_change_trace_unreg(void);
+
+/*
  * Tracepoints for VM enters
  */
 DECLARE_EVENT_CLASS(kvm_transition,
@@ -303,6 +310,36 @@ TRACE_EVENT(kvm_guestid_change,
 		      __entry->guestid)
 );
 
+TRACE_EVENT_FN(kvm_guest_mode_change,
+	    TP_PROTO(struct kvm_vcpu *vcpu),
+	    TP_ARGS(vcpu),
+	    TP_STRUCT__entry(
+			__field(unsigned long, epc)
+			__field(unsigned long, pc)
+			__field(unsigned long, badvaddr)
+			__field(unsigned int, status)
+			__field(unsigned int, cause)
+	    ),
+
+	    TP_fast_assign(
+			__entry->epc = kvm_read_c0_guest_epc(vcpu->arch.cop0);
+			__entry->pc = vcpu->arch.pc;
+			__entry->badvaddr = kvm_read_c0_guest_badvaddr(vcpu->arch.cop0);
+			__entry->status = kvm_read_c0_guest_status(vcpu->arch.cop0);
+			__entry->cause = kvm_read_c0_guest_cause(vcpu->arch.cop0);
+	    ),
+
+	    TP_printk("EPC: 0x%08lx PC: 0x%08lx Status: 0x%08x Cause: 0x%08x BadVAddr: 0x%08lx",
+		      __entry->epc,
+		      __entry->pc,
+		      __entry->status,
+		      __entry->cause,
+		      __entry->badvaddr),
+
+	    kvm_guest_mode_change_trace_reg,
+	    kvm_guest_mode_change_trace_unreg
+);
+
 #endif /* _TRACE_KVM_H */
 
 /* This part must be outside protection */
diff --git a/arch/mips/kvm/vz.c b/arch/mips/kvm/vz.c
index 44dad9ae5d02..33bb8c6e1b05 100644
--- a/arch/mips/kvm/vz.c
+++ b/arch/mips/kvm/vz.c
@@ -1322,6 +1322,18 @@ static enum emulation_result kvm_trap_vz_handle_gsfc(u32 cause, u32 *opc,
 	return er;
 }
 
+static enum emulation_result kvm_trap_vz_handle_ghfc(u32 cause, u32 *opc,
+						     struct kvm_vcpu *vcpu)
+{
+	/*
+	 * Presumably this is due to MC (guest mode change), so lets trace some
+	 * relevant info.
+	 */
+	trace_kvm_guest_mode_change(vcpu);
+
+	return EMULATE_DONE;
+}
+
 static enum emulation_result kvm_trap_vz_handle_hc(u32 cause, u32 *opc,
 						   struct kvm_vcpu *vcpu)
 {
@@ -1407,8 +1419,7 @@ static int kvm_trap_vz_handle_guest_exit(struct kvm_vcpu *vcpu)
 		break;
 	case MIPS_GCTL0_GEXC_GHFC:
 		++vcpu->stat.vz_ghfc_exits;
-		er = kvm_trap_vz_no_handler_guest_exit(gexccode, cause, opc,
-						       vcpu);
+		er = kvm_trap_vz_handle_ghfc(cause, opc, vcpu);
 		break;
 	case MIPS_GCTL0_GEXC_GPA:
 		++vcpu->stat.vz_gpa_exits;
@@ -2459,6 +2470,12 @@ static int kvm_vz_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 	 */
 	kvm_vz_restore_timer(vcpu);
 
+	/* Set MC bit if we want to trace guest mode changes */
+	if (kvm_trace_guest_mode_change)
+		set_c0_guestctl0(MIPS_GCTL0_MC);
+	else
+		clear_c0_guestctl0(MIPS_GCTL0_MC);
+
 	/* Don't bother restoring registers multiple times unless necessary */
 	if (!all)
 		return 0;