The calculation of the upper limit for queues does not depend solely on
the number of possible CPUs; for example, the isolcpus kernel
command-line option must also be considered.

To account for this, the block layer provides a helper function to
retrieve the maximum number of queues. Use it to set an appropriate
upper queue number limit.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Daniel Wagner <wagi@kernel.org>
---
 drivers/nvme/host/pci.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 8ff12e415cb5d1529d760b33f3e0cf3b8d1555f1..f134bf4f41b2581e4809e618250de7985b5c9701 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -97,7 +97,7 @@ static int io_queue_count_set(const char *val, const struct kernel_param *kp)
 	int ret;
 
 	ret = kstrtouint(val, 10, &n);
-	if (ret != 0 || n > num_possible_cpus())
+	if (ret != 0 || n > blk_mq_num_possible_queues(0))
 		return -EINVAL;
 	return param_set_uint(val, kp);
 }
@@ -2520,7 +2520,8 @@ static unsigned int nvme_max_io_queues(struct nvme_dev *dev)
 	 */
 	if (dev->ctrl.quirks & NVME_QUIRK_SHARED_TAGS)
 		return 1;
-	return num_possible_cpus() + dev->nr_write_queues + dev->nr_poll_queues;
+	return blk_mq_num_possible_queues(0) + dev->nr_write_queues +
+		dev->nr_poll_queues;
 }
 
 static int nvme_setup_io_queues(struct nvme_dev *dev)

-- 
2.49.0

On 6/17/25 06:43, Daniel Wagner wrote:
> The calculation of the upper limit for queues does not depend solely on
> the number of possible CPUs; for example, the isolcpus kernel
> command-line option must also be considered.
>
> To account for this, the block layer provides a helper function to
> retrieve the maximum number of queues. Use it to set an appropriate
> upper queue number limit.
>
> Reviewed-by: Christoph Hellwig<hch@lst.de>
> Reviewed-by: Hannes Reinecke<hare@suse.de>
> Signed-off-by: Daniel Wagner<wagi@kernel.o

Thanks a lot for this it really makes code clean with a new helper
which shows association with queue than open coded cpu helper.

Looks good.

Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>

-ck