x86/vector: Add vector domain debugfs support

Add the debug callback for the vector domain, which gives a detailed
information about vector usage if invoked for the domain by using rhe
matrix allocator debug function and vector/target information when invoked
for a particular interrupt.

Extra information foir the Vector domain:

Online bitmaps:       32
Global available:   6352
Global reserved:       5
Total allocated:      20
System: 41: 0-19,32,50,128,238-255
 | CPU | avl | man | act | vectors
     0   183     4    19  33-48,51-53
     1   199     4     1  33
     2   199     4     0  

Extra information for interrupts:

     Vector:    42
     Target:     4

This allows a detailed analysis of the vector usage and the association to
interrupts and devices.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juergen Gross <jgross@suse.com>
Tested-by: Yu Chen <yu.c.chen@intel.com>
Acked-by: Juergen Gross <jgross@suse.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Alok Kataria <akataria@vmware.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Rui Zhang <rui.zhang@intel.com>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Len Brown <lenb@kernel.org>
Link: https://lkml.kernel.org/r/20170913213155.188137174@linutronix.de

arch/x86/kernel/apic/vector.c

@@ -11,6 +11,7 @@
  * published by the Free Software Foundation.
  */
 #include <linux/interrupt.h>
+#include <linux/seq_file.h>
 #include <linux/init.h>
 #include <linux/compiler.h>
 #include <linux/slab.h>
@@ -373,9 +374,54 @@ error:
 	return err;
 }
 
+#ifdef CONFIG_GENERIC_IRQ_DEBUGFS
+void x86_vector_debug_show(struct seq_file *m, struct irq_domain *d,
+			   struct irq_data *irqd, int ind)
+{
+	unsigned int cpu, vec, prev_cpu, prev_vec;
+	struct apic_chip_data *apicd;
+	unsigned long flags;
+	int irq;
+
+	if (!irqd) {
+		irq_matrix_debug_show(m, vector_matrix, ind);
+		return;
+	}
+
+	irq = irqd->irq;
+	if (irq < nr_legacy_irqs() && !test_bit(irq, &io_apic_irqs)) {
+		seq_printf(m, "%*sVector: %5d\n", ind, "", ISA_IRQ_VECTOR(irq));
+		seq_printf(m, "%*sTarget: Legacy PIC all CPUs\n", ind, "");
+		return;
+	}
+
+	apicd = irqd->chip_data;
+	if (!apicd) {
+		seq_printf(m, "%*sVector: Not assigned\n", ind, "");
+		return;
+	}
+
+	raw_spin_lock_irqsave(&vector_lock, flags);
+	cpu = apicd->cpu;
+	vec = apicd->cfg.vector;
+	prev_cpu = apicd->prev_cpu;
+	prev_vec = apicd->cfg.old_vector;
+	raw_spin_unlock_irqrestore(&vector_lock, flags);
+	seq_printf(m, "%*sVector: %5u\n", ind, "", vec);
+	seq_printf(m, "%*sTarget: %5u\n", ind, "", cpu);
+	if (prev_vec) {
+		seq_printf(m, "%*sPrevious vector: %5u\n", ind, "", prev_vec);
+		seq_printf(m, "%*sPrevious target: %5u\n", ind, "", prev_cpu);
+	}
+}
+#endif
+
 static const struct irq_domain_ops x86_vector_domain_ops = {
-	.alloc	= x86_vector_alloc_irqs,
-	.free	= x86_vector_free_irqs,
+	.alloc		= x86_vector_alloc_irqs,
+	.free		= x86_vector_free_irqs,
+#ifdef CONFIG_GENERIC_IRQ_DEBUGFS
+	.debug_show	= x86_vector_debug_show,
+#endif
 };
 
 int __init arch_probe_nr_irqs(void)