diff --git a/src/arch/arm/isa/insts/misc.isa b/src/arch/arm/isa/insts/misc.isa
index 9ee753e385..35b310ecb9 100644
--- a/src/arch/arm/isa/insts/misc.isa
+++ b/src/arch/arm/isa/insts/misc.isa
@@ -848,7 +848,8 @@ let {{
     '''
     unknownIop = ArmInstObjParams("unknown", "Unknown", "UnknownOp", \
                                   { "code": unknownCode,
-                                    "predicate_test": predicateTest })
+                                    "predicate_test": predicateTest },
+                                  ['IsInvalid'])
     header_output += BasicDeclare.subst(unknownIop)
     decoder_output += BasicConstructor.subst(unknownIop)
     exec_output += PredOpExecute.subst(unknownIop)
diff --git a/src/arch/arm/isa/insts/misc64.isa b/src/arch/arm/isa/insts/misc64.isa
index 5678195415..266467e9d8 100644
--- a/src/arch/arm/isa/insts/misc64.isa
+++ b/src/arch/arm/isa/insts/misc64.isa
@@ -183,7 +183,7 @@ let {{
             return std::make_shared<UndefinedInstruction>(machInst, true);
     '''
     unknown64Iop = ArmInstObjParams("unknown", "Unknown64", "UnknownOp64",
-                                    unknownCode)
+                                    unknownCode, ['IsInvalid'])
     header_output += BasicDeclare.subst(unknown64Iop)
     decoder_output += BasicConstructor64.subst(unknown64Iop)
     exec_output += BasicExecute.subst(unknown64Iop)
diff --git a/src/arch/mips/isa/formats/unknown.isa b/src/arch/mips/isa/formats/unknown.isa
index 8d3ccdfef1..782b4e1595 100644
--- a/src/arch/mips/isa/formats/unknown.isa
+++ b/src/arch/mips/isa/formats/unknown.isa
@@ -47,6 +47,7 @@ output header {{
             // don't call execute() (which panics) if we're on a
             // speculative path
             flags[IsNonSpeculative] = true;
+            flags[IsInvalid] = true;
         }
 
         Fault execute(ExecContext *, trace::InstRecord *) const override;
diff --git a/src/arch/power/isa/formats/unknown.isa b/src/arch/power/isa/formats/unknown.isa
index 85dacc5796..78eac5ca8b 100644
--- a/src/arch/power/isa/formats/unknown.isa
+++ b/src/arch/power/isa/formats/unknown.isa
@@ -49,6 +49,7 @@ output header {{
             // don't call execute() (which panics) if we're on a
             // speculative path
             flags[IsNonSpeculative] = true;
+            flags[IsInvalid] = true;
         }
 
         Fault execute(ExecContext *, trace::InstRecord *) const override;
diff --git a/src/arch/riscv/insts/unknown.hh b/src/arch/riscv/insts/unknown.hh
index 64f94dea00..ca90c453f5 100644
--- a/src/arch/riscv/insts/unknown.hh
+++ b/src/arch/riscv/insts/unknown.hh
@@ -54,7 +54,9 @@ class Unknown : public RiscvStaticInst
   public:
     Unknown(ExtMachInst _machInst)
         : RiscvStaticInst("unknown", _machInst, No_OpClass)
-    {}
+    {
+        flags[IsInvalid] = true;
+    }
 
     Fault
     execute(ExecContext *, trace::InstRecord *) const override
diff --git a/src/arch/sparc/insts/unknown.hh b/src/arch/sparc/insts/unknown.hh
index f4bb143198..f5e4b70d43 100644
--- a/src/arch/sparc/insts/unknown.hh
+++ b/src/arch/sparc/insts/unknown.hh
@@ -47,7 +47,9 @@ class Unknown : public SparcStaticInst
     // Constructor
     Unknown(ExtMachInst _machInst) :
             SparcStaticInst("unknown", _machInst, No_OpClass)
-    {}
+    {
+        flags[IsInvalid] = true;
+    }
 
     Fault
     execute(ExecContext *, trace::InstRecord *) const override
diff --git a/src/arch/x86/isa/formats/unknown.isa b/src/arch/x86/isa/formats/unknown.isa
index eca297bab2..d7bca54cd1 100644
--- a/src/arch/x86/isa/formats/unknown.isa
+++ b/src/arch/x86/isa/formats/unknown.isa
@@ -53,6 +53,7 @@ output header {{
         Unknown(ExtMachInst _machInst) :
                 X86ISA::X86StaticInst("unknown", _machInst, No_OpClass)
         {
+            flags[IsInvalid] = true;
         }
 
         Fault execute(ExecContext *, trace::InstRecord *) const override;
diff --git a/src/cpu/StaticInstFlags.py b/src/cpu/StaticInstFlags.py
index 4ab6cc499c..2e02833d1a 100644
--- a/src/cpu/StaticInstFlags.py
+++ b/src/cpu/StaticInstFlags.py
@@ -99,4 +99,5 @@ class StaticInstFlags(Enum):
         "IsHtmStart",  # Starts a HTM transaction
         "IsHtmStop",  # Stops (commits) a HTM transaction
         "IsHtmCancel",  # Explicitely aborts a HTM transaction
+        "IsInvalid",  # An invalid instruction
     ]
diff --git a/src/cpu/static_inst.hh b/src/cpu/static_inst.hh
index 12b05f9b0e..78e47f4ed8 100644
--- a/src/cpu/static_inst.hh
+++ b/src/cpu/static_inst.hh
@@ -196,6 +196,8 @@ class StaticInst : public RefCounted, public StaticInstFlags
     bool isHtmStop() const { return flags[IsHtmStop]; }
     bool isHtmCancel() const { return flags[IsHtmCancel]; }
 
+    bool isInvalid() const { return flags[IsInvalid]; }
+
     bool
     isHtmCmd() const
     {