[PATCH] nvme-core: avoid identify with CNS 06h to discovery controller

[PATCH] nvme-core: avoid identify with CNS 06h to discovery controller

[Martin George]

nvme_init_non_mdts_limits() currenty invokes an identify command with
CNS 06h to both discovery and i/o controllers. But as per the NVMe-oF
specification, this is not supported on discovery controllers:

"The Discovery controller shall support the Identify command with a
CNS value of 01h (Identify Controller data structure); all other CNS
values are reserved."

So ensure this identify command with CNS 06h is sent to i/o controllers
alone and not to discovery controllers.

Signed-off-by: Martin George <marting@netapp.com>
---
 drivers/nvme/host/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index d4be525f8100..62d1048c6506 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -3063,7 +3063,7 @@ static int nvme_init_non_mdts_limits(struct nvme_ctrl *ctrl)
 	else
 		ctrl->max_zeroes_sectors = 0;
 
-	if (nvme_ctrl_limited_cns(ctrl))
+	if (nvme_ctrl_limited_cns(ctrl) || nvme_discovery_ctrl(ctrl))
 		return 0;
 
 	id = kzalloc(sizeof(*id), GFP_KERNEL);
-- 
2.34.1

Re: [PATCH] nvme-core: avoid identify with CNS 06h to discovery controller

[Christoph Hellwig]

On Sat, Mar 11, 2023 at 10:56:03PM +0530, Martin George wrote:
> nvme_init_non_mdts_limits() currenty invokes an identify command with
> CNS 06h to both discovery and i/o controllers. But as per the NVMe-oF
> specification, this is not supported on discovery controllers:
> 
> "The Discovery controller shall support the Identify command with a
> CNS value of 01h (Identify Controller data structure); all other CNS
> values are reserved."
> 
> So ensure this identify command with CNS 06h is sent to i/o controllers
> alone and not to discovery controllers.

This looks correct, but can we go a step further and also skip it
for administrative controllers, i.e

> -	if (nvme_ctrl_limited_cns(ctrl))
> +	if (nvme_ctrl_limited_cns(ctrl) || nvme_discovery_ctrl(ctrl))

	if (ctrl->subsys->subtype != NVME_NQN_NVME ||
	    nvme_ctrl_limited_cns(ctrl))

?

Re: [PATCH] nvme-core: avoid identify with CNS 06h to discovery controller

[Martin George]

On Wed, 2023-03-15 at 06:47 -0700, Christoph Hellwig wrote:
> On Sat, Mar 11, 2023 at 10:56:03PM +0530, Martin George wrote:
> > nvme_init_non_mdts_limits() currenty invokes an identify command
> > with
> > CNS 06h to both discovery and i/o controllers. But as per the NVMe-
> > oF
> > specification, this is not supported on discovery controllers:
> > 
> > "The Discovery controller shall support the Identify command with a
> > CNS value of 01h (Identify Controller data structure); all other
> > CNS
> > values are reserved."
> > 
> > So ensure this identify command with CNS 06h is sent to i/o
> > controllers
> > alone and not to discovery controllers.
> 
> This looks correct, but can we go a step further and also skip it
> for administrative controllers, i.e
> 
> > -       if (nvme_ctrl_limited_cns(ctrl))
> > +       if (nvme_ctrl_limited_cns(ctrl) ||
> > nvme_discovery_ctrl(ctrl))
> 
>         if (ctrl->subsys->subtype != NVME_NQN_NVME ||
>             nvme_ctrl_limited_cns(ctrl))
> 
> ?

Sure. Will send a new patch for the same.

-Martin