nvme-pci: initialize queue memory before interrupts

BugLink: https://bugs.launchpad.net/bugs/1784409

commit 161b8be2 upstream.

A spurious interrupt before the nvme driver has initialized the completion
queue may inadvertently cause the driver to believe it has a completion
to process. This may result in a NULL dereference since the nvmeq's tags
are not set at this point.

The patch initializes the host's CQ memory so that a spurious interrupt
isn't mistaken for a real completion.
Signed-off-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
[bwh: Backported to 4.4: adjust context]
Cc: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

drivers/nvme/host/pci.c

@@ -1341,11 +1341,11 @@ static int nvme_create_queue(struct nvme_queue *nvmeq, int qid)
 	if (result < 0)
 		goto release_cq;
 
+	nvme_init_queue(nvmeq, qid);
 	result = queue_request_irq(dev, nvmeq, nvmeq->irqname);
 	if (result < 0)
 		goto release_sq;
 
-	nvme_init_queue(nvmeq, qid);
 	return result;
 
  release_sq:
@@ -1464,6 +1464,7 @@ static int nvme_configure_admin_queue(struct nvme_dev *dev)
 		goto free_nvmeq;
 
 	nvmeq->cq_vector = 0;
+	nvme_init_queue(nvmeq, 0);
 	result = queue_request_irq(dev, nvmeq, nvmeq->irqname);
 	if (result) {
 		nvmeq->cq_vector = -1;
@@ -2064,7 +2065,6 @@ static void nvme_reset_work(struct work_struct *work)
 	if (result)
 		goto unmap;
 
-	nvme_init_queue(dev->queues[0], 0);
 	result = nvme_alloc_admin_tags(dev);
 	if (result)
 		goto disable;