From: Keith Busch <keith.busch@intel.com>
Date: Wed, 6 Jun 2018 08:13:09 -0600
Subject: [PATCH] nvme-pci: make CMB SQ mod-param read-only
Git-commit: 69f4eb9ff79556c1a3daf5af5573594c196f30cc
Patch-mainline: v4.18-rc1
References: bsc#1104967,FATE#325924

A controller reset after a run time change of the CMB module parameter
breaks the driver. An 'on -> off' will have the driver use NULL for the
host memory queue, and 'off -> on' will use mismatched queue depth between
the device and the host.

We could fix both, but there isn't really a good reason to change this
at run time anyway, compared to at module load time, so this patch makes
parameter read-only after after modprobe.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Hannes Reinecke <hare@suse.com>
---
 drivers/nvme/host/pci.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index d935aba0288f..cd7aec58a301 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -42,7 +42,7 @@ static int use_threaded_interrupts;
 module_param(use_threaded_interrupts, int, 0);
 
 static bool use_cmb_sqes = true;
-module_param(use_cmb_sqes, bool, 0644);
+module_param(use_cmb_sqes, bool, 0444);
 MODULE_PARM_DESC(use_cmb_sqes, "use controller's memory buffer for I/O SQes");
 
 static unsigned int max_host_mem_size_mb = 128;
-- 
2.16.4