Re: [PATCH RFC 1/3] nvmet: add command quiesce time

[Mohamed Khalfella <mkhalfella@purestorage.com>]

On 2025-03-24 13:07:56 +0100, Daniel Wagner wrote:
> TP4129 introduces Command Quiesce Time (CQT) for coordinating the
> shutdown sequence when for example KATO expires.
> 
> Add support to nvmet but only report CQT is available but the controller
> doesn't need any additional time when shutting down. In this case the
> spec says nvmet should report a value of 1.
> 
> Signed-off-by: Daniel Wagner <wagi@kernel.org>
> ---
>  drivers/nvme/target/admin-cmd.c | 6 ++++++
>  drivers/nvme/target/nvmet.h     | 1 +
>  include/linux/nvme.h            | 4 +++-
>  3 files changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/nvme/target/admin-cmd.c b/drivers/nvme/target/admin-cmd.c
> index e670dc185a967dc69c9b7d23930bb52bdcc3271a..09ac5a43f70dbe3889c1b404d6b59c0053337192 100644
> --- a/drivers/nvme/target/admin-cmd.c
> +++ b/drivers/nvme/target/admin-cmd.c
> @@ -733,6 +733,12 @@ static void nvmet_execute_identify_ctrl(struct nvmet_req *req)
>  	/* We support keep-alive timeout in granularity of seconds */
>  	id->kas = cpu_to_le16(NVMET_KAS);
>  
> +	/*
> +	 * Command Quiesce Time in milliseconds. If the controller is not
> +	 * need any quiencse time, the controller should set it to 1.
> +	 */
> +	id->cqt = cpu_to_le16(NVMET_CQT);
> +
>  	id->sqes = (0x6 << 4) | 0x6;
>  	id->cqes = (0x4 << 4) | 0x4;
>  
> diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
> index b540216c0c9a9138f0913f8df28fa5ae13c6397f..47ae8be6200054eaaad2dbacf23db080bf0c56c2 100644
> --- a/drivers/nvme/target/nvmet.h
> +++ b/drivers/nvme/target/nvmet.h
> @@ -671,6 +671,7 @@ bool nvmet_subsys_nsid_exists(struct nvmet_subsys *subsys, u32 nsid);
>  
>  #define NVMET_KAS		10
>  #define NVMET_DISC_KATO_MS		120000
> +#define NVMET_CQT		1

Setting CQT to 1 is a promise to initiator that target will quiesce
pending requests in 1ms after it detects loss of kato traffic. For
initiator, it means these requests can be retried safely in 1m after
kato delay. Is this guaranteed by target?

I thought leaving the value 0 means CQT is not implemented, no?

>  
>  int __init nvmet_init_configfs(void);
>  void __exit nvmet_exit_configfs(void);
> diff --git a/include/linux/nvme.h b/include/linux/nvme.h
> index fe3b60818fdcfbb4baabce59f7499bc1fa07e855..983b047e7158dcb33da66a25c67684b8f1ef5a7e 100644
> --- a/include/linux/nvme.h
> +++ b/include/linux/nvme.h
> @@ -335,7 +335,9 @@ struct nvme_id_ctrl {
>  	__u8			anacap;
>  	__le32			anagrpmax;
>  	__le32			nanagrpid;
> -	__u8			rsvd352[160];
> +	__u8			rsvd352[34];
> +	__u16			cqt;
> +	__u8			rsvd388[124];
>  	__u8			sqes;
>  	__u8			cqes;
>  	__le16			maxcmd;
> 
> -- 
> 2.48.1
>