Patch "nvme-fabrics: handle zero MAXCMD without closing the connection" has been added to the 6.12-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    nvme-fabrics: handle zero MAXCMD without closing the connection

to the 6.12-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     nvme-fabrics-handle-zero-maxcmd-without-closing-the-.patch
and it can be found in the queue-6.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 921d457ef162fc451de6498529068ab9931d3219
Author: Maurizio Lombardi <mlombard@xxxxxxxxxx>
Date:   Fri Nov 29 15:17:06 2024 +0100

    nvme-fabrics: handle zero MAXCMD without closing the connection
    
    [ Upstream commit 88c23a32b851e36adc4ab36f796d9b711f47e2bb ]
    
    The NVMe specification states that MAXCMD is mandatory
    for NVMe-over-Fabrics implementations. However, some NVMe/TCP
    and NVMe/FC arrays from major vendors have buggy firmware
    that reports MAXCMD as zero in the Identify Controller data structure.
    
    Currently, the implementation closes the connection in such cases,
    completely preventing the host from connecting to the target.
    
    Fix the issue by printing a clear error message about the firmware bug
    and allowing the connection to proceed. It assumes that the
    target supports a MAXCMD value of SQSIZE + 1. If any issues arise,
    the user can manually adjust SQSIZE to mitigate them.
    
    Fixes: 4999568184e5 ("nvme-fabrics: check max outstanding commands")
    Signed-off-by: Maurizio Lombardi <mlombard@xxxxxxxxxx>
    Reviewed-by: Laurence Oberman <loberman@xxxxxxxxxx>
    Reviewed-by: Christoph Hellwig <hch@xxxxxx>
    Signed-off-by: Keith Busch <kbusch@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index fe83d31ac928b..ec03b25eacbbc 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -3251,8 +3251,9 @@ static int nvme_check_ctrl_fabric_info(struct nvme_ctrl *ctrl, struct nvme_id_ct
 	}
 
 	if (!ctrl->maxcmd) {
-		dev_err(ctrl->device, "Maximum outstanding commands is 0\n");
-		return -EINVAL;
+		dev_warn(ctrl->device,
+			"Firmware bug: maximum outstanding commands is 0\n");
+		ctrl->maxcmd = ctrl->sqsize + 1;
 	}
 
 	return 0;