blk-mq: provide a default queue mapping for PCI device

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 45 insertions, 0 deletions

diff --git a/block/blk-mq-pci.c b/block/blk-mq-pci.c
new file mode 100644
index 000000000000..33c7bd743c63
--- /dev/null
+++ b/block/blk-mq-pci.c
@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2016 Christoph Hellwig.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ */
+#include <linux/blk-mq.h>
+#include <linux/blk-mq-pci.h>
+#include <linux/pci.h>
+#include <linux/module.h>
+
+/**
+ * blk_mq_pci_map_queues - provide a default queue mapping for PCI device
+ * @set:        tagset to provide the mapping for
+ * @pdev:       PCI device associated with @set.
+ *
+ * This function assumes the PCI device @pdev has at least as many available
+ * interrupt vetors as @set has queues.  It will then queuery 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.
+ */
+int blk_mq_pci_map_queues(struct blk_mq_tag_set *set, struct pci_dev *pdev)
+{
+        const struct cpumask *mask;
+        unsigned int queue, cpu;
+
+        for (queue = 0; queue < set->nr_hw_queues; queue++) {
+                mask = pci_irq_get_affinity(pdev, queue);
+                if (!mask)
+                        return -EINVAL;
+
+                for_each_cpu(cpu, mask)
+                        set->mq_map[cpu] = queue;
+        }
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(blk_mq_pci_map_queues);