nvme/pcie: increase min admin queue size to 256

Now that IO qpairs can be created asynchronously, we need to make sure
that all the create IO CQ/SQ commands can be executed simultaneously.
It is pretty common to create multiple IO qpairs at the same time, e.g.
adding an NVMe bdev to an nvmf subsystem will create an IO qpair on each
poll group.  In that case, if the number of cores exceed the size of the
admin queue (actually it can be even lower due to outstanding AERs), we
might run out nvme_requests on the admin queue.

The chosen minimum value for the admin queue size, 256, should be enough
to cover most cases.

Fixes #2465

Signed-off-by: Konrad Sztyber <konrad.sztyber@intel.com>
Change-Id: I55c59aef64f3fdb33f7b4824d3e9beb403602633
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/12270
Community-CI: Broadcom CI <spdk-ci.pdl@broadcom.com>
Community-CI: Mellanox Build Bot
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Shuhei Matsumoto <smatsumoto@nvidia.com>
Reviewed-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>

lib/nvme/nvme_pcie.c

@@ -932,6 +932,8 @@ static struct spdk_nvme_ctrlr *nvme_pcie_ctrlr_construct(const struct spdk_nvme_
 	pctrlr->devhandle = devhandle;
 	pctrlr->ctrlr.opts = *opts;
 	pctrlr->ctrlr.trid = *trid;
+	pctrlr->ctrlr.opts.admin_queue_size = spdk_max(pctrlr->ctrlr.opts.admin_queue_size,
+					      NVME_PCIE_MIN_ADMIN_QUEUE_SIZE);
 
 	rc = nvme_ctrlr_construct(&pctrlr->ctrlr);
 	if (rc != 0) {

lib/nvme/nvme_pcie_internal.h

@@ -49,6 +49,9 @@
 
 #define NVME_MAX_PRP_LIST_ENTRIES	(503)
 
+/* Minimum admin queue size */
+#define NVME_PCIE_MIN_ADMIN_QUEUE_SIZE	(256)
+
 /* PCIe transport extensions for spdk_nvme_ctrlr */
 struct nvme_pcie_ctrlr {
 	struct spdk_nvme_ctrlr ctrlr;

lib/nvme/nvme_vfio_user.c

@@ -204,6 +204,8 @@ static struct spdk_nvme_ctrlr *
 	pctrlr->ctrlr.opts = *opts;
 	pctrlr->ctrlr.trid = *trid;
 	pctrlr->ctrlr.opts.use_cmb_sqs = false;
+	pctrlr->ctrlr.opts.admin_queue_size = spdk_max(pctrlr->ctrlr.opts.admin_queue_size,
+					      NVME_PCIE_MIN_ADMIN_QUEUE_SIZE);
 
 	ret = nvme_ctrlr_construct(&pctrlr->ctrlr);
 	if (ret != 0) {