[RFC PATCH v3 04/32] x86/traps: add external_interrupt() to dispatch external interrupts

[Xin Li <xin3.li@intel.com>]

From: "H. Peter Anvin (Intel)" <hpa@zytor.com>

Add external_interrupt() to dispatch external interrupts to their
handlers. If an external interrupt is a system interrupt, dipatch
it through system_interrupt_handler_table, otherwise call into
dispatch_common_interrupt().

Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Co-developed-by: Xin Li <xin3.li@intel.com>
Signed-off-by: Xin Li <xin3.li@intel.com>
---
 arch/x86/kernel/traps.c | 41 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index c0f7666140da..31ad645be2fb 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -1499,6 +1499,47 @@ void __init install_system_interrupt_handler(unsigned int n, const void *asm_add
 	alloc_intr_gate(n, asm_addr);
 }
 
+#ifndef CONFIG_X86_LOCAL_APIC
+/*
+ * Used when local APIC is not compiled into the kernel, but
+ * external_interrupt() needs dispatch_spurious_interrupt().
+ */
+DEFINE_IDTENTRY_IRQ(spurious_interrupt)
+{
+	pr_info("Spurious interrupt (vector 0x%x) on CPU#%d, should never happen.\n",
+		vector, smp_processor_id());
+}
+#endif
+
+/*
+ * External interrupt dispatch function.
+ *
+ * Until/unless dispatch_common_interrupt() can be taught to deal with the
+ * special system vectors, split the dispatch.
+ *
+ * Note: dispatch_common_interrupt() already deals with IRQ_MOVE_CLEANUP_VECTOR.
+ */
+int external_interrupt(struct pt_regs *regs, unsigned int vector)
+{
+	unsigned int sysvec = vector - FIRST_SYSTEM_VECTOR;
+
+	if (vector < FIRST_EXTERNAL_VECTOR) {
+		pr_err("invalid external interrupt vector %d\n", vector);
+		return -EINVAL;
+	}
+
+	if (sysvec < NR_SYSTEM_VECTORS) {
+		if (system_interrupt_handlers[sysvec])
+			system_interrupt_handlers[sysvec](regs);
+		else
+			dispatch_spurious_interrupt(regs, vector);
+	} else {
+		dispatch_common_interrupt(regs, vector);
+	}
+
+	return 0;
+}
+
 void __init trap_init(void)
 {
 	/* Init cpu_entry_area before IST entries are set up */
-- 
2.34.1