x86/apic: Split out spurious handling code

sysvec_spurious_apic_interrupt() calls into the handling body of
__spurious_interrupt() which is not obvious as that function is declared
inside the DEFINE_IDTENTRY_IRQ(spurious_interrupt) macro.

As __spurious_interrupt() is currently always inlined this ends up with two
copies of the same code for no reason.

Split the handling function out and invoke it from both entry points.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210210002512.469379641@linutronix.de

arch/x86/kernel/apic/apic.c

@@ -2133,18 +2133,11 @@ void __init register_lapic_address(unsigned long address)
  * Local APIC interrupts
  */
 
-/**
- * spurious_interrupt - Catch all for interrupts raised on unused vectors
- * @regs:	Pointer to pt_regs on stack
- * @vector:	The vector number
- *
- * This is invoked from ASM entry code to catch all interrupts which
- * trigger on an entry which is routed to the common_spurious idtentry
- * point.
- *
- * Also called from sysvec_spurious_apic_interrupt().
+/*
+ * Common handling code for spurious_interrupt and spurious_vector entry
+ * points below. No point in allowing the compiler to inline it twice.
  */
-DEFINE_IDTENTRY_IRQ(spurious_interrupt)
+static noinline void handle_spurious_interrupt(u8 vector)
 {
 	u32 v;
 
@@ -2179,9 +2172,23 @@ DEFINE_IDTENTRY_IRQ(spurious_interrupt)
 	trace_spurious_apic_exit(vector);
 }
 
+/**
+ * spurious_interrupt - Catch all for interrupts raised on unused vectors
+ * @regs:	Pointer to pt_regs on stack
+ * @vector:	The vector number
+ *
+ * This is invoked from ASM entry code to catch all interrupts which
+ * trigger on an entry which is routed to the common_spurious idtentry
+ * point.
+ */
+DEFINE_IDTENTRY_IRQ(spurious_interrupt)
+{
+	handle_spurious_interrupt(vector);
+}
+
 DEFINE_IDTENTRY_SYSVEC(sysvec_spurious_apic_interrupt)
 {
-	__spurious_interrupt(regs, SPURIOUS_APIC_VECTOR);
+	handle_spurious_interrupt(SPURIOUS_APIC_VECTOR);
 }
 
 /*