diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index bd43866f9c3e..57c891148b59 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -546,8 +546,8 @@ __visible noinstr void func(struct pt_regs *regs,			\
  */
 	.align IDT_ALIGN
 SYM_CODE_START(irq_entries_start)
-    vector=FIRST_EXTERNAL_VECTOR
-    .rept NR_EXTERNAL_VECTORS
+    vector=FIRST_EXTERNAL_VECTOR_IDT
+    .rept FIRST_SYSTEM_VECTOR - FIRST_EXTERNAL_VECTOR_IDT
 	UNWIND_HINT_IRET_REGS
 0 :
 	ENDBR
diff --git a/arch/x86/include/asm/irq.h b/arch/x86/include/asm/irq.h
index 768aa234cbb4..e4be6f8409ad 100644
--- a/arch/x86/include/asm/irq.h
+++ b/arch/x86/include/asm/irq.h
@@ -11,6 +11,11 @@
 #include <asm/apicdef.h>
 #include <asm/irq_vectors.h>
 
+/*
+ * The first available IRQ vector
+ */
+extern unsigned int __ro_after_init first_external_vector;
+
 /*
  * The irq entry code is in the noinstr section and the start/end of
  * __irqentry_text is emitted via labels. Make the build fail if
diff --git a/arch/x86/include/asm/irq_vectors.h b/arch/x86/include/asm/irq_vectors.h
index 43dcb9284208..cb3670a7c18f 100644
--- a/arch/x86/include/asm/irq_vectors.h
+++ b/arch/x86/include/asm/irq_vectors.h
@@ -31,15 +31,23 @@
 
 /*
  * IDT vectors usable for external interrupt sources start at 0x20.
- * (0x80 is the syscall vector, 0x30-0x3f are for ISA)
+ * (0x80 is the syscall vector, 0x30-0x3f are for ISA).
+ *
+ * With FRED we can also use 0x10-0x1f even though those overlap
+ * exception vectors as FRED distinguishes exceptions and interrupts.
+ * Therefore, FIRST_EXTERNAL_VECTOR is no longer a constant.
  */
-#define FIRST_EXTERNAL_VECTOR		0x20
+#define FIRST_EXTERNAL_VECTOR_IDT	0x20
+#define FIRST_EXTERNAL_VECTOR_FRED	0x10
+#define FIRST_EXTERNAL_VECTOR		first_external_vector
 
 /*
  * Reserve the lowest usable vector (and hence lowest priority)  0x20 for
  * triggering cleanup after irq migration. 0x21-0x2f will still be used
  * for device interrupts.
  */
+#define IRQ_MOVE_CLEANUP_VECTOR_IDT	FIRST_EXTERNAL_VECTOR_IDT
+#define IRQ_MOVE_CLEANUP_VECTOR_FRED	FIRST_EXTERNAL_VECTOR_FRED
 #define IRQ_MOVE_CLEANUP_VECTOR		FIRST_EXTERNAL_VECTOR
 
 #define IA32_SYSCALL_VECTOR		0x80
@@ -48,7 +56,7 @@
  * Vectors 0x30-0x3f are used for ISA interrupts.
  *   round up to the next 16-vector boundary
  */
-#define ISA_IRQ_VECTOR(irq)		(((FIRST_EXTERNAL_VECTOR + 16) & ~15) + irq)
+#define ISA_IRQ_VECTOR(irq)		(((FIRST_EXTERNAL_VECTOR_IDT + 16) & ~15) + irq)
 
 /*
  * Special IRQ vectors used by the SMP architecture, 0xf0-0xff
@@ -114,7 +122,6 @@
 #define FIRST_SYSTEM_VECTOR		NR_VECTORS
 #endif
 
-#define NR_EXTERNAL_VECTORS		(FIRST_SYSTEM_VECTOR - FIRST_EXTERNAL_VECTOR)
 #define NR_SYSTEM_VECTORS		(NR_VECTORS - FIRST_SYSTEM_VECTOR)
 
 /*
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 20d9a604da7c..eef67f64aa81 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1621,12 +1621,17 @@ static void setup_local_APIC(void)
 	/*
 	 * Set Task Priority to 'accept all except vectors 0-31'.  An APIC
 	 * vector in the 16-31 range could be delivered if TPR == 0, but we
-	 * would think it's an exception and terrible things will happen.  We
-	 * never change this later on.
+	 * would think it's an exception and terrible things will happen,
+	 * unless we are using FRED in which case interrupts and
+	 * exceptions are distinguished by type code.
+	 *
+	 * We never change this later on.
 	 */
+	BUG_ON(!first_external_vector);
+
 	value = apic_read(APIC_TASKPRI);
 	value &= ~APIC_TPRI_MASK;
-	value |= 0x10;
+	value |= (first_external_vector - 0x10) & APIC_TPRI_MASK;
 	apic_write(APIC_TASKPRI, value);
 
 	/* Clear eventually stale ISR/IRR bits */
diff --git a/arch/x86/kernel/apic/vector.c b/arch/x86/kernel/apic/vector.c
index c1efebd27e6c..f4325445fd78 100644
--- a/arch/x86/kernel/apic/vector.c
+++ b/arch/x86/kernel/apic/vector.c
@@ -46,6 +46,7 @@ static struct irq_matrix *vector_matrix;
 #ifdef CONFIG_SMP
 static DEFINE_PER_CPU(struct hlist_head, cleanup_list);
 #endif
+unsigned int first_external_vector = FIRST_EXTERNAL_VECTOR_IDT;
 
 void lock_vector_lock(void)
 {
@@ -796,7 +797,12 @@ int __init arch_early_irq_init(void)
 	 * Allocate the vector matrix allocator data structure and limit the
 	 * search area.
 	 */
-	vector_matrix = irq_alloc_matrix(NR_VECTORS, FIRST_EXTERNAL_VECTOR,
+	if (cpu_feature_enabled(X86_FEATURE_FRED))
+		first_external_vector = FIRST_EXTERNAL_VECTOR_FRED;
+	else
+		first_external_vector = FIRST_EXTERNAL_VECTOR_IDT;
+
+	vector_matrix = irq_alloc_matrix(NR_VECTORS, first_external_vector,
 					 FIRST_SYSTEM_VECTOR);
 	BUG_ON(!vector_matrix);
 
diff --git a/arch/x86/kernel/fred.c b/arch/x86/kernel/fred.c
index 907abfd69f3f..8d6dda8c8e71 100644
--- a/arch/x86/kernel/fred.c
+++ b/arch/x86/kernel/fred.c
@@ -56,7 +56,7 @@ void __init fred_setup_apic(void)
 {
 	int i;
 
-	for (i = 0; i < FIRST_EXTERNAL_VECTOR; i++)
+	for (i = 0; i < FIRST_EXTERNAL_VECTOR_FRED; i++)
 		set_bit(i, system_vectors);
 
 	/*
@@ -65,7 +65,7 @@ void __init fred_setup_apic(void)
 	 * /proc/interrupts.
 	 */
 #ifdef CONFIG_SMP
-	set_bit(IRQ_MOVE_CLEANUP_VECTOR, system_vectors);
+	set_bit(IRQ_MOVE_CLEANUP_VECTOR_FRED, system_vectors);
 #endif
 
 	for (i = 0; i < NR_SYSTEM_VECTORS; i++) {
diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c
index a58c6bc1cd68..d3fd86f85de9 100644
--- a/arch/x86/kernel/idt.c
+++ b/arch/x86/kernel/idt.c
@@ -131,7 +131,7 @@ static const __initconst struct idt_data apic_idts[] = {
 	INTG(RESCHEDULE_VECTOR,			asm_sysvec_reschedule_ipi),
 	INTG(CALL_FUNCTION_VECTOR,		asm_sysvec_call_function),
 	INTG(CALL_FUNCTION_SINGLE_VECTOR,	asm_sysvec_call_function_single),
-	INTG(IRQ_MOVE_CLEANUP_VECTOR,		asm_sysvec_irq_move_cleanup),
+	INTG(IRQ_MOVE_CLEANUP_VECTOR_IDT,	asm_sysvec_irq_move_cleanup),
 	INTG(REBOOT_VECTOR,			asm_sysvec_reboot),
 #endif
 
@@ -274,13 +274,13 @@ static void __init idt_map_in_cea(void)
  */
 void __init idt_setup_apic_and_irq_gates(void)
 {
-	int i = FIRST_EXTERNAL_VECTOR;
+	int i = FIRST_EXTERNAL_VECTOR_IDT;
 	void *entry;
 
 	idt_setup_from_table(idt_table, apic_idts, ARRAY_SIZE(apic_idts), true);
 
 	for_each_clear_bit_from(i, system_vectors, FIRST_SYSTEM_VECTOR) {
-		entry = irq_entries_start + IDT_ALIGN * (i - FIRST_EXTERNAL_VECTOR);
+		entry = irq_entries_start + IDT_ALIGN * (i - FIRST_EXTERNAL_VECTOR_IDT);
 		set_intr_gate(i, entry);
 	}
 
diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index 7e125fff45ab..b7511e02959c 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -359,7 +359,7 @@ void fixup_irqs(void)
 	 * vector_lock because the cpu is already marked !online, so
 	 * nothing else will touch it.
 	 */
-	for (vector = FIRST_EXTERNAL_VECTOR; vector < NR_VECTORS; vector++) {
+	for (vector = first_external_vector; vector < NR_VECTORS; vector++) {
 		if (IS_ERR_OR_NULL(__this_cpu_read(vector_irq[vector])))
 			continue;
 
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index ecfaf4d647bb..73471053ed02 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -1489,6 +1489,8 @@ DEFINE_IDTENTRY_IRQ(spurious_interrupt)
 	pr_info("Spurious interrupt (vector 0x%x) on CPU#%d, should never happen.\n",
 		vector, smp_processor_id());
 }
+
+unsigned int first_external_vector = FIRST_EXTERNAL_VECTOR_IDT;
 #endif
 
 static void dispatch_table_spurious_interrupt(struct pt_regs *regs)
