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Date:   Thu, 9 May 2019 10:23:34 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     Aya Levin <ayal@...lanox.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Eran Ben Elisha <eranbe@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Jiri Pirko <jiri@...lanox.com>
Subject: Re: [PATCH net-next RFC] Dump SW SQ context as part of tx reporter

Tue, May 07, 2019 at 02:58:32PM CEST, ayal@...lanox.com wrote:
>
>
>On 5/7/2019 3:41 PM, Jiri Pirko wrote:
>> Mon, Apr 29, 2019 at 04:17:39PM CEST, ayal@...lanox.com wrote:
>>> TX reporter reports an error on two scenarios:
>>> - TX timeout on a specific tx queue
>>> - TX completion error on a specific send queue
>>> Prior to this patch, no dump data was supported by the tx reporter. This
>>> patch adds support for SW data dump of the related SQ context. The dump
>>> is simply the SQ's raw memory snapshot taken right after the error was
>>> reported, before any recovery procedure was launched. With this
>>> approach, no maintenance is needed as the driver fetch the actual data
>>> according to the layout on which the SQ was compiled with.  By providing
>>> a SW context, one can easily debug error on a given SQ.
>>>
>>> In order to offline translate the raw memory into a human readable
>>> format, the user can use some out-of-kernel scripts which receives as an
>>> input the following:
>>> - Object raw memory
>>> - Driver object compiled with debug info (can be taken/generated at any time from the machine)
>>> - Object name
>>>
>>> An example of such script output can be seen below.
>>> Note: the script is not offered as part of this patch as it do not
>>> belong to the kernel, I just described it in order to grasp the general
>>> idea of how/what can be fetched from SW dump via devlink health.
>>>
>>> The output of the SW dump can be extracted by devlink health command:
>>> $ sudo devlink health dump show pci/0000:00:0b.0 reporter tx.
>>> mlx5e_txqsq: sqn: 6336
>>> memory:
>>>    00 00 00 00 00 00 00 00
>>>    01 00 00 00 00 00 00 00
>>>    00 00 00 00 00 00 00 00
>>>    45 f4 88 cb 09 00 00 00
>>>    00 00 00 00 00 00 00 00
>>>    00 00 00 00 00 00 00 00
>>>    c0 ff ff ff 1f 00 00 00
>>>    f8 18 1e 89 81 88 ff ff
>>>    ...
>>>
>>> script output below, with struct members names and actual values:
>>>
>>> struct  mlx5e_txqsq {
>>> 	short unsigned int         cc 	 0x5 ;
>>> 	unsigned int               dma_fifo_cc 	 0x5 ;
>>> 	struct  net_dim {
>>> 		unsigned char      state 	 0x1 ;
>>> 		struct  net_dim_stats {
>>> 			int        ppms 	 0x0 ;
>>> 			int        bpms 	 0x0 ;
>>> 			int        epms 	 0x0 ;
>>> 		} prev_stats;
>>> 		struct  net_dim_sample {
>>> 			long long int time 	 0x90766ef9d ;
>>> 			unsigned int pkt_ctr 	 0x0 ;
>>> 			unsigned int byte_ctr 	 0x0 ;
>>> 			short unsigned int event_ctr 	 0x0 ;
>>> 		} start_sample;
>>> 		struct  work_struct {
>>> 			struct   {
>>> 				long int counter 	 0x1fffffffc0 ;
>>> 			} data;
>>> 			struct  list_head {
>>> 				struct list_head * next 	 0xffff8881b08998f8 ;
>>> 				struct list_head * prev 	 0xffff8881b08998f8 ;
>>> 			} entry;
>>> 			void       (*func)(struct work_struct *) 	 0xffffffffa02d0e30 ;
>>> 		} work;
>>> 		unsigned char      profile_ix 	 0x60 ;
>>> 		unsigned char      mode 	 0x72 ;
>>> 		unsigned char      tune_state 	 0x35 ;
>>> 		unsigned char      steps_right 	 0xa0 ;
>>> 		unsigned char      steps_left 	 0xff ;
>>> 		unsigned char      tired 	 0xff ;
>>> 	} dim;
>>> 	short unsigned int         pc 	 0x0 ;
>>> 	unsigned int               dma_fifo_pc 	 0x0 ;
>>> 	struct  mlx5e_cq {
>>> 		struct  mlx5_cqwq {
>>> 			struct  mlx5_frag_buf_ctrl {
>>> 				struct mlx5_buf_list * frags 	 0x500000005 ;
>>> 				unsigned int sz_m1 	 0x0 ;
>>> 				short unsigned int frag_sz_m1 	 0x0 ;
>>> 				short unsigned int strides_offset 	 0x0 ;
>>> 				unsigned char log_sz 	 0x0 ;
>>> 				unsigned char log_stride 	 0x0 ;
>>> 				unsigned char log_frag_strides 	 0x0 ;
>>> 			} fbc;
>>> 			__be32 *   db 	 0x0 ;
>>> 			unsigned int cc 	 0x0 ;
>>> 		} wq;
>>> 		short unsigned int event_ctr 	 0x0 ;
>>> 		struct napi_struct * napi 	 0x0 ;
>>> 		struct  mlx5_core_cq {
>>> 			unsigned int cqn 	 0x0 ;
>>> 			int        cqe_sz 	 0x0 ;
>>> 			__be32 *   set_ci_db 	 0xffff8881b1aa4988 ;
>>> 			__be32 *   arm_db 	 0x3f000003ff ;
>>> 			struct mlx5_uars_page * uar 	 0x6060a ;
>>> 			struct  refcount_struct {
>>> 				struct   {
>>> 					int    counter 	 0xa1814500 ;
>>> 				} refs;
>>> 			} refcount;
>>> 			struct  completion {
>>> 				unsigned int done 	 0x5 ;
>>> 				struct  wait_queue_head {
>>> 					struct  spinlock {
>>> 						union   {
>>> 							struct  raw_spinlock {
>>> 								struct  qspinlock {
>>> 									union   {
>>> 										struct   {
>>> 											int                                                    counter 	 0x5 ;
>>> 										} val;
>>> 										struct   {
>>> 											unsigned char                                          locked 	 0x5 ;
>>> 											unsigned char                                          pending 	 0x0 ;
>>> 										} ;
>>> 										struct   {
>>> 											short unsigned int                                     locked_pending 	 0x5 ;
>>> 											short unsigned int                                     tail 	 0x0 ;
>>> 										} ;
>>> 									} ;
>>> 								} raw_lock;
>>> 							} rlock;
>>> 						} ;
>>> 					} lock;
>>> 					struct  list_head {
>>> 						struct list_head * next 	 0xffff8881b089bb88 ;
>>> 						struct list_head * prev 	 0x4000000c0a ;
>>> 					} head;
>>> 				} wait;
>>> 			} free;
>>> 			unsigned int vector 	 0xa1814500 ;
>>> 			unsigned int irqn 	 0xffff8881 ;
>>> 			void       (*comp)(struct mlx5_core_cq *) 	 0xffff8881a1814504 ;
>>> 			void       (*event)(struct mlx5_core_cq *, enum mlx5_event) 	 0xffff8881a2cdea08 ;
>>> 			unsigned int cons_index 	 0x1 ;
>>> 			unsigned int arm_sn 	 0x0 ;
>>> 			struct mlx5_rsc_debug * dbg 	 0x0 ;
>>> 			int        pid 	 0x0 ;
>>> 			struct   {
>>> 				struct  list_head {
>>> 					struct list_head * next 	 0xffffffff ;
>>> 					struct list_head * prev 	 0xffffffffffffffff ;
>>> 				} list;
>>> 				void (*comp)(struct mlx5_core_cq *) 	 0xffffffffa0356940 ;
>>> 				void * priv 	 0x0 ;
>>> 			} tasklet_ctx;
>>> 			int        reset_notify_added 	 0x0 ;
>>> 			struct  list_head {
>>> 				struct list_head * next 	 0xffffffffa0300700 ;
>>> 				struct list_head * prev 	 0xd ;
>>> 			} reset_notify;
>>> 			struct mlx5_eq_comp * eq 	 0x0 ;
>>> 			short unsigned int uid 	 0x9a70 ;
>>> 		} mcq;
>>> 		struct mlx5e_channel * channel 	 0xffff8881b0899a70 ;
>>> 		struct mlx5_core_dev * mdev 	 0x4800000001 ;
>>> 		struct  mlx5_wq_ctrl {
>>> 			struct mlx5_core_dev * mdev 	 0xffffffffa02d5350 ;
>>> 			struct  mlx5_frag_buf {
>>> 				struct mlx5_buf_list * frags 	 0xffffffffa02d5460 ;
>>> 				int npages 	 0x0 ;
>>> 				int size 	 0x5 ;
>>> 				unsigned char page_shift 	 0x8 ;
>>> 			} buf;
>>> 			struct  mlx5_db {
>>> 				__be32 * db 	 0x1c6 ;
>>> 				union   {
>>> 					struct mlx5_db_pgdir * pgdir 	 0x0 ;
>>> 					struct mlx5_ib_user_db_page * user_page 	 0x0 ;
>>> 				} u;
>>> 				long long unsigned int dma 	 0xffff8881b0899ab0 ;
>>> 				int index 	 0x0 ;
>>> 			} db;
>>> 		} wq_ctrl;
>>> 	} cq;
>>> 	struct  mlx5_wq_cyc {
>>> 		struct  mlx5_frag_buf_ctrl {
>>> 			struct mlx5_buf_list * frags 	 0xffff8881a7600160 ;
>>> 			unsigned int sz_m1 	 0xa7600160 ;
>>> 			short unsigned int frag_sz_m1 	 0x8881 ;
>>> 			short unsigned int strides_offset 	 0xffff ;
>>> 			unsigned char log_sz 	 0x88 ;
>>> 			unsigned char log_stride 	 0x49 ;
>>> 			unsigned char log_frag_strides 	 0xaa ;
>>> 		} fbc;
>>> 		__be32 *           db 	 0x1000000000010 ;
>>> 		short unsigned int sz 	 0xc ;
>>> 		short unsigned int wqe_ctr 	 0x0 ;
>>> 		short unsigned int cur_sz 	 0x0 ;
>>> 	} wq;
>>> 	unsigned int               dma_fifo_mask 	 0xa1814500 ;
>>> 	struct mlx5e_sq_stats *    stats 	 0xffff8881a33a0348 ;
>>> 	struct   {
>>> 		struct mlx5e_sq_dma * dma_fifo 	 0x1a1814500 ;
>>> 		struct mlx5e_tx_wqe_info * wqe_info 	 0x14 ;
>>> 	} db;
>>> 	void *                     uar_map 	 0x0 ;
>>> 	struct netdev_queue *      txq 	 0x0 ;
>>> 	unsigned int               sqn 	 0x18c0 ;
>>> 	unsigned char              min_inline_mode 	 0x0 ;
>>> 	struct device *            pdev 	 0x0 ;
>>> 	unsigned int               mkey_be 	 0x0 ;
>>> 	long unsigned int          state 	 0x0 ;
>>> 	struct hwtstamp_config *   tstamp 	 0x0 ;
>>> 	struct mlx5_clock *        clock 	 0xffff8881b1aa6f88 ;
>>> 	struct  mlx5_wq_ctrl {
>>> 		struct mlx5_core_dev * mdev 	 0x3f000003ff ;
>>> 		struct  mlx5_frag_buf {
>>> 			struct mlx5_buf_list * frags 	 0x6060a ;
>>> 			int        npages 	 0xa1814604 ;
>>> 			int        size 	 0xffff8881 ;
>>> 			unsigned char page_shift 	 0x0 ;
>>> 		} buf;
>>> 		struct  mlx5_db {
>>> 			__be32 *   db 	 0xfff ;
>>> 			union   {
>>> 				struct mlx5_db_pgdir * pgdir 	 0x0 ;
>>> 				struct mlx5_ib_user_db_page * user_page 	 0x0 ;
>>> 			} u;
>>> 			long long unsigned int dma 	 0xffff888188440000 ;
>>> 			int        index 	 0x8b074000 ;
>>> 		} db;
>>> 	} wq_ctrl;
>>> 	struct mlx5e_channel *     channel 	 0xffffc9000010d800 ;
>>> 	int                        txq_ix 	 0xa0020180 ;
>>> 	unsigned int               rate_limit 	 0xffff8881 ;
>>> 	struct  work_struct {
>>> 		struct   {
>>> 			long int   counter 	 0x1000018c0 ;
>>> 		} data;
>>> 		struct  list_head {
>>> 			struct list_head * next 	 0xffff8881c32b68e8 ;
>>> 			struct list_head * prev 	 0x800 ;
>>> 		} entry;
>>> 		void               (*func)(struct work_struct *) 	 0x9 ;
>>> 	} recover_work;
>>> } ;
>> 
>> I don't get it. You are dumping live kernel memory? There are already
>> facilities to do that in place. Why to replicate it?
>I am dumping the driver's memory under a lock so I can ensure it's 
>consistency (as appose to /dev/mem)
>vmcore cannot be taken from a live kernel (without crashing).
>I need the memory's snapshot right after the error from the driver's 
>context.

Got it. However, this sounds like a generic problem not specific to
nic drivers. How other subsystems resolve this (if they do at all)?



>Which other tools do you mean?
>> 
>> 
>>>
>>> Signed-off-by: Aya Levin <ayal@...lanox.com>
>>> ---
>>> .../ethernet/mellanox/mlx5/core/en/reporter_tx.c   | 100 +++++++++++++++++++++
>>> 1 file changed, 100 insertions(+)
>>>
>>> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/reporter_tx.c b/drivers/net/ethernet/mellanox/mlx5/core/en/reporter_tx.c
>>> index 476dd97f7f2f..8a39f5525e57 100644
>>> --- a/drivers/net/ethernet/mellanox/mlx5/core/en/reporter_tx.c
>>> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en/reporter_tx.c
>>> @@ -9,6 +9,7 @@
>>>
>>> struct mlx5e_tx_err_ctx {
>>> 	int (*recover)(struct mlx5e_txqsq *sq);
>>> +	int (*dump)(struct mlx5e_txqsq *sq);
>>> 	struct mlx5e_txqsq *sq;
>>> };
>>>
>>> @@ -281,10 +282,109 @@ static int mlx5e_tx_reporter_diagnose(struct devlink_health_reporter *reporter,
>>> 	return err;
>>> }
>>>
>>> +static int mlx5e_tx_reporter_sw_dump_from_ctx(struct mlx5e_priv *priv,
>>> +					      struct mlx5e_txqsq *sq,
>>> +					      struct devlink_fmsg *fmsg)
>>> +{
>>> +	u64 *ptr = (u64 *)sq;
>>> +	int copy, err;
>>> +	int i = 0;
>>> +
>>> +	if (!test_bit(MLX5E_STATE_OPENED, &priv->state))
>>> +		return 0;
>>> +
>>> +	err = devlink_fmsg_pair_nest_start(fmsg, "mlx5e_txqsq");
>>> +	if (err)
>>> +		return err;
>>> +
>>> +	err = devlink_fmsg_obj_nest_start(fmsg);
>>> +	if (err)
>>> +		return err;
>>> +
>>> +	err = devlink_fmsg_arr_pair_nest_start(fmsg, "memory");
>>> +	if (err)
>>> +		return err;
>>> +
>>> +	while (i < sizeof(struct mlx5e_txqsq)) {
>>> +		copy = sizeof(u64);
>>> +
>>> +		if (i + copy > sizeof(struct mlx5e_txqsq))
>>> +			copy = sizeof(struct mlx5e_txqsq) - i;
>>> +
>>> +		err = devlink_fmsg_binary_put(fmsg, ptr, copy);
>>> +		if (err)
>>> +			return err;
>>> +		ptr++;
>>> +		i += copy;
>>> +	}
>>> +
>>> +	err = devlink_fmsg_arr_pair_nest_end(fmsg);
>>> +	if (err)
>>> +		return err;
>>> +
>>> +	err = devlink_fmsg_obj_nest_end(fmsg);
>>> +	if (err)
>>> +		return err;
>>> +
>>> +	err = devlink_fmsg_pair_nest_end(fmsg);
>>> +
>>> +	return err;
>>> +}
>>> +
>>> +static int mlx5e_tx_reporter_sw_dump_all(struct mlx5e_priv *priv,
>>> +					 struct devlink_fmsg *fmsg)
>>> +{
>>> +	int i, err = 0;
>>> +
>>> +	mutex_lock(&priv->state_lock);
>>> +
>>> +	if (!test_bit(MLX5E_STATE_OPENED, &priv->state))
>>> +		goto unlock;
>>> +
>>> +	err = devlink_fmsg_arr_pair_nest_start(fmsg, "SQs");
>>> +	if (err)
>>> +		goto unlock;
>>> +
>>> +	for (i = 0; i < priv->channels.num * priv->channels.params.num_tc;
>>> +	     i++) {
>>> +		err = devlink_fmsg_obj_nest_start(fmsg);
>>> +		if (err)
>>> +			goto unlock;
>>> +
>>> +		err = mlx5e_tx_reporter_sw_dump_from_ctx(priv, priv->txq2sq[i],
>>> +							 fmsg);
>>> +		if (err)
>>> +			goto unlock;
>>> +
>>> +		err = devlink_fmsg_pair_nest_end(fmsg);
>>> +		if (err)
>>> +			goto unlock;
>>> +	}
>>> +	err = devlink_fmsg_arr_pair_nest_end(fmsg);
>>> +	if (err)
>>> +		goto unlock;
>>> +
>>> +unlock:
>>> +	mutex_unlock(&priv->state_lock);
>>> +	return err;
>>> +}
>>> +
>>> +static int mlx5e_tx_reporter_sw_dump(struct devlink_health_reporter *reporter,
>>> +				     struct devlink_fmsg *fmsg, void *context)
>>> +{
>>> +	struct mlx5e_priv *priv = devlink_health_reporter_priv(reporter);
>>> +	struct mlx5e_tx_err_ctx *err_ctx = context;
>>> +
>>> +	return err_ctx ? mlx5e_tx_reporter_sw_dump_from_ctx(priv, err_ctx->sq,
>>> +							    fmsg) :
>>> +			 mlx5e_tx_reporter_sw_dump_all(priv, fmsg);
>>> +}
>>> +
>>> static const struct devlink_health_reporter_ops mlx5_tx_reporter_ops = {
>>> 		.name = "tx",
>>> 		.recover = mlx5e_tx_reporter_recover,
>>> 		.diagnose = mlx5e_tx_reporter_diagnose,
>>> +		.dump = mlx5e_tx_reporter_sw_dump,
>>> };
>>>
>>> #define MLX5_REPORTER_TX_GRACEFUL_PERIOD 500
>>> -- 
>>> 2.14.1
>>>

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