From: Long Li <longli@microsoft.com>
Date: Fri, 6 Sep 2019 10:24:20 -0700
Patch-mainline: v5.4-rc2
Subject: scsi: storvsc: setup 1:1 mapping between hardware queue and CPU queue
Git-commit: 0ed8810276907c8a633dc8cecc48dabb6678cd23
References: bsc#1140729

storvsc doesn't use a dedicated hardware queue for a given CPU queue. When
issuing I/O, it selects returning CPU (hardware queue) dynamically based on
vmbus channel usage across all channels.

This patch advertises num_present_cpus() as number of hardware queues. This
will have upper layer setup 1:1 mapping between hardware queue and CPU
queue and avoid unnecessary locking when issuing I/O.

Link: https://lore.kernel.org/r/1567790660-48142-1-git-send-email-longli@linuxonhyperv.com
Signed-off-by: Long Li <longli@microsoft.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Acked-by: Olaf Hering <ohering@suse.de>
---
 drivers/scsi/storvsc_drv.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
--- a/drivers/scsi/storvsc_drv.c
+++ b/drivers/scsi/storvsc_drv.c
@@ -1837,8 +1837,7 @@ static int storvsc_probe(struct hv_device *device,
 	/*
 	 * Set the number of HW queues we are supporting.
 	 */
-	if (stor_device->num_sc != 0)
-		host->nr_hw_queues = stor_device->num_sc + 1;
+	host->nr_hw_queues = num_present_cpus();
 
 	/*
 	 * Set the error handler work queue.