genirq/msi: Capture device name for debugfs

For debugging the allocation of unused or potentially leaked interrupt
descriptor it's helpful to have some information about the site which
allocated them. In case of MSI this is simple because the caller hands the
device struct pointer into the domain allocation function.

Duplicate the device name and show it in the debugfs entry of the interrupt
descriptor.
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/20170913213152.433038426@linutronix.de

include/linux/irqdesc.h

@@ -93,6 +93,7 @@ struct irq_desc {
 #endif
 #ifdef CONFIG_GENERIC_IRQ_DEBUGFS
 	struct dentry		*debugfs_file;
+	const char		*dev_name;
 #endif
 #ifdef CONFIG_SPARSE_IRQ
 	struct rcu_head		rcu;

kernel/irq/debugfs.c

@@ -149,6 +149,7 @@ static int irq_debug_show(struct seq_file *m, void *p)
 	raw_spin_lock_irq(&desc->lock);
 	data = irq_desc_get_irq_data(desc);
 	seq_printf(m, "handler:  %pf\n", desc->handle_irq);
+	seq_printf(m, "device:   %s\n", desc->dev_name);
 	seq_printf(m, "status:   0x%08x\n", desc->status_use_accessors);
 	irq_debug_show_bits(m, 0, desc->status_use_accessors, irqdesc_states,
 			    ARRAY_SIZE(irqdesc_states));
@@ -226,6 +227,15 @@ static const struct file_operations dfs_irq_ops = {
 	.release	= single_release,
 };
 
+void irq_debugfs_copy_devname(int irq, struct device *dev)
+{
+	struct irq_desc *desc = irq_to_desc(irq);
+	const char *name = dev_name(dev);
+
+	if (name)
+		desc->dev_name = kstrdup(name, GFP_KERNEL);
+}
+
 void irq_add_debugfs_entry(unsigned int irq, struct irq_desc *desc)
 {
 	char name [10];

kernel/irq/internals.h

@@ -443,7 +443,9 @@ void irq_add_debugfs_entry(unsigned int irq, struct irq_desc *desc);
 static inline void irq_remove_debugfs_entry(struct irq_desc *desc)
 {
 	debugfs_remove(desc->debugfs_file);
+	kfree(desc->dev_name);
 }
+void irq_debugfs_copy_devname(int irq, struct device *dev);
 # ifdef CONFIG_IRQ_DOMAIN
 void irq_domain_debugfs_init(struct dentry *root);
 # else
@@ -458,4 +460,7 @@ static inline void irq_add_debugfs_entry(unsigned int irq, struct irq_desc *d)
 static inline void irq_remove_debugfs_entry(struct irq_desc *d)
 {
 }
+static inline void irq_debugfs_copy_devname(int irq, struct device *dev)
+{
+}
 #endif /* CONFIG_GENERIC_IRQ_DEBUGFS */

kernel/irq/msi.c

@@ -16,6 +16,8 @@
 #include <linux/msi.h>
 #include <linux/slab.h>
 
+#include "internals.h"
+
 /**
  * alloc_msi_entry - Allocate an initialize msi_entry
  * @dev:	Pointer to the device for which this is allocated
@@ -373,8 +375,10 @@ int msi_domain_alloc_irqs(struct irq_domain *domain, struct device *dev,
 			return ret;
 		}
 
-		for (i = 0; i < desc->nvec_used; i++)
+		for (i = 0; i < desc->nvec_used; i++) {
 			irq_set_msi_desc_off(virq, i, desc);
+			irq_debugfs_copy_devname(virq + i, dev);
+		}
 	}
 
 	if (ops->msi_finish)