linux-kernel - Re: [PATCH 1/2] nvme: only allow entering LIVE from CONNECTING state

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Message-ID: <8574c297-fc02-40d6-ba67-ab43e3d5e394@redhat.com>
Date: Fri, 9 Jan 2026 14:18:13 -0500
From: John Meneghini <jmeneghi@...hat.com>
To: Daniel Wagner <wagi@...nel.org>, Keith Busch <kbusch@...nel.org>,
 Jens Axboe <axboe@...nel.dk>, Christoph Hellwig <hch@....de>,
 Sagi Grimberg <sagi@...mberg.me>, James Smart <james.smart@...adcom.com>,
 Hannes Reinecke <hare@...e.de>,
 Shinichiro Kawasaki <shinichiro.kawasaki@....com>,
 Nilay Shroff <nilay@...ux.ibm.com>, Wen Xiong <wenxiong@...ux.ibm.com>,
 Narayana Murty N <nnmlinux@...ux.ibm.com>
Cc: linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org,
 Ewan Milne <emilne@...hat.com>, Maurizio Lombardi <mlombard@...hat.com>
Subject: Re: [PATCH 1/2] nvme: only allow entering LIVE from CONNECTING state

Unfortunately, it has been discovered that this patch causes a serious regression on powerpc platforms.

If anyone has a powerpc platform with an NVMe/PCIe device installed, please run this simple test and see if it works.

# uname -av
Linux rdma-cert-03-lp10.rdma.lab.eng.rdu2.redhat.com 6.19.0-rc4+ #1 SMP Wed Jan  7 21:42:54 EST 2026 ppc64le GNU/Linux

# nvme list-subsys /dev/nvme0n1
nvme-subsys0 - NQN=nqn.1994-11.com.samsung:nvme:PM1735:HHHL:S4WANA0R400032
                hostnqn=nqn.2014-08.org.nvmexpress:uuid:1654a627-93b6-4650-ba90-f4dc7a2fd3ee
                iopolicy=numa
\
  +- nvme0 pcie 0018:01:00.0 live optimized

# nvme subsystem-reset /dev/nvme0; nvme list-subsys /dev/nvme0n1; sleep 1; nvme list-subsys /dev/nvme0n1; nvme list-subsys /dev/nvme0n1;
nvme-subsys0 - NQN=nqn.1994-11.com.samsung:nvme:PM1735:HHHL:S4WANA0R400032
                hostnqn=nqn.2014-08.org.nvmexpress:uuid:1654a627-93b6-4650-ba90-f4dc7a2fd3ee
                iopolicy=numa
\
  +- nvme0 pcie 0018:01:00.0 resetting optimized
[Wed Jan  7 21:59:51 2026] block nvme0n1: no usable path - requeuing I/O
[Wed Jan  7 21:59:51 2026] block nvme0n1: no usable path - requeuing I/O
[Wed Jan  7 21:59:51 2026] block nvme0n1: no usable path - requeuing I/O
[Wed Jan  7 21:59:51 2026] block nvme0n1: no usable path - requeuing I/O
[Wed Jan  7 21:59:51 2026] block nvme0n1: no usable path - requeuing I/O

# nvme list-subsys /dev/nvme0n1;

# nvme list-subsys /dev/nvme0n1;
nvme-subsys0 - NQN=nqn.1994-11.com.samsung:nvme:PM1735:HHHL:S4WANA0R400032
                hostnqn=nqn.2014-08.org.nvmexpress:uuid:1654a627-93b6-4650-ba90-f4dc7a2fd3ee
                iopolicy=numa
\
  +- nvme0 pcie 0018:01:00.0 resetting optimized

At this point the machine is HUNG. It's stuck in the resetting state forever.

Because /dev/nvme0n1 is the root device, I need to power-cycle/reboot the host to recover.
/John

On 2/14/25 3:02 AM, Daniel Wagner wrote:
> The fabric transports and also the PCI transport are not entering the
> LIVE state from NEW or RESETTING. This makes the state machine more
> restrictive and allows to catch not supported state transitions, e.g.
> directly switching from RESETTING to LIVE.
> 
> Signed-off-by: Daniel Wagner <wagi@...nel.org>
> ---
>   drivers/nvme/host/core.c | 2 --
>   1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index 818d4e49aab51c388af9a48bf9d466fea9cef51b..f028913e2e622ee348e88879c6e6b7e8f8a1cc82 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -564,8 +564,6 @@ bool nvme_change_ctrl_state(struct nvme_ctrl *ctrl,
>   	switch (new_state) {
>   	case NVME_CTRL_LIVE:
>   		switch (old_state) {
> -		case NVME_CTRL_NEW:
> -		case NVME_CTRL_RESETTING:
>   		case NVME_CTRL_CONNECTING:
>   			changed = true;
>   			fallthrough;
>