nvme-pci: Separate IO and admin queue IRQ vectors

The admin and first IO queues shared the first irq vector, which has an
affinity mask including cpu0. If a system allows cpu0 to be offlined,
the admin queue may not be usable if no other CPUs in the affinity mask
are online. This is a problem since unlike IO queues, there is only
one admin queue that always needs to be usable.

To fix, this patch allocates one pre_vector for the admin queue that
is assigned all CPUs, so will always be accessible. The IO queues are
assigned the remaining managed vectors.

In case a controller has only one interrupt vector available, the admin
and IO queues will share the pre_vector with all CPUs assigned.

Cc: Jianchao Wang <jianchao.w.wang@oracle.com>
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 0b3b4d9fd423a8ab0e9d5915951d1171f6bf5882..fbc71fac6f1e077ad21d336c8e8ca3e3bc311cbe 100644 (file)
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -84,6 +84,7 @@ struct nvme_dev {
        struct dma_pool *prp_small_pool;
        unsigned online_queues;
        unsigned max_qid;
+       unsigned int num_vecs;
        int q_depth;
        u32 db_stride;
        void __iomem *bar;
@@ -414,7 +415,8 @@ static int nvme_pci_map_queues(struct blk_mq_tag_set *set)
 {
        struct nvme_dev *dev = set->driver_data;
 
-       return blk_mq_pci_map_queues(set, to_pci_dev(dev->dev), 0);
+       return blk_mq_pci_map_queues(set, to_pci_dev(dev->dev),
+                       dev->num_vecs > 1 ? 1 /* admin queue */ : 0);
 }
 
 /**
@@ -1456,7 +1458,11 @@ static int nvme_create_queue(struct nvme_queue *nvmeq, int qid)
                nvmeq->sq_cmds_io = dev->cmb + offset;
        }
 
-       nvmeq->cq_vector = qid - 1;
+       /*
+        * A queue's vector matches the queue identifier unless the controller
+        * has only one vector available.
+        */
+       nvmeq->cq_vector = dev->num_vecs == 1 ? 0 : qid;
        result = adapter_alloc_cq(dev, qid, nvmeq);
        if (result < 0)
                goto release_vector;
@@ -1910,6 +1916,10 @@ static int nvme_setup_io_queues(struct nvme_dev *dev)
        int result, nr_io_queues;
        unsigned long size;
 
+       struct irq_affinity affd = {
+               .pre_vectors = 1
+       };
+
        nr_io_queues = num_possible_cpus();
        result = nvme_set_queue_count(&dev->ctrl, &nr_io_queues);
        if (result < 0)
@@ -1945,11 +1955,12 @@ static int nvme_setup_io_queues(struct nvme_dev *dev)
         * setting up the full range we need.
         */
        pci_free_irq_vectors(pdev);
-       nr_io_queues = pci_alloc_irq_vectors(pdev, 1, nr_io_queues,
-                       PCI_IRQ_ALL_TYPES | PCI_IRQ_AFFINITY);
-       if (nr_io_queues <= 0)
+       result = pci_alloc_irq_vectors_affinity(pdev, 1, nr_io_queues + 1,
+                       PCI_IRQ_ALL_TYPES | PCI_IRQ_AFFINITY, &affd);
+       if (result <= 0)
                return -EIO;
-       dev->max_qid = nr_io_queues;
+       dev->num_vecs = result;
+       dev->max_qid = max(result - 1, 1);
 
        /*
         * Should investigate if there's a performance win from allocating