1 files changed, 47 insertions, 0 deletions
diff --git a/block/blk-mq-pci.c b/block/blk-mq-pci.c
new file mode 100644
index 000000000..a90b88fd1
--- /dev/null
+++ b/block/blk-mq-pci.c
@@ -0,0 +1,47 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2016 Christoph Hellwig.
+ */
+#include <linux/kobject.h>
+#include <linux/blkdev.h>
+#include <linux/blk-mq.h>
+#include <linux/blk-mq-pci.h>
+#include <linux/pci.h>
+#include <linux/module.h>
+
+#include "blk-mq.h"
+
+/**
+ * blk_mq_pci_map_queues - provide a default queue mapping for PCI device
+ * @qmap:	CPU to hardware queue map.
+ * @pdev:	PCI device associated with @set.
+ * @offset:	Offset to use for the pci irq vector
+ *
+ * This function assumes the PCI device @pdev has at least as many available
+ * interrupt vectors as @set has queues.  It will then query the vector
+ * corresponding to each queue for it's affinity mask and built queue mapping
+ * that maps a queue to the CPUs that have irq affinity for the corresponding
+ * vector.
+ */
+void blk_mq_pci_map_queues(struct blk_mq_queue_map *qmap, struct pci_dev *pdev,
+			   int offset)
+{
+	const struct cpumask *mask;
+	unsigned int queue, cpu;
+
+	for (queue = 0; queue < qmap->nr_queues; queue++) {
+		mask = pci_irq_get_affinity(pdev, queue + offset);
+		if (!mask)
+			goto fallback;
+
+		for_each_cpu(cpu, mask)
+			qmap->mq_map[cpu] = qmap->queue_offset + queue;
+	}
+
+	return;
+
+fallback:
+	WARN_ON_ONCE(qmap->nr_queues > 1);
+	blk_mq_clear_mq_map(qmap);
+}
+EXPORT_SYMBOL_GPL(blk_mq_pci_map_queues);