Subject: Re: [PATCH net-next RFC] Dump SW SQ context as part of tx reporter

From: Jiri Pirko <[email-masked]>
Date: Tue, 14 May 2019 14:07:51 +0200

Sun, May 12, 2019 at 10:37:35AM CEST, [email-masked] wrote:
>
>
>On 5/9/2019 11:23 AM, Jiri Pirko wrote:
>> Tue, May 07, 2019 at 02:58:32PM CEST, [email-masked] wrote:
>>>
>>>
>>> On 5/7/2019 3:41 PM, Jiri Pirko wrote:
>>>> Mon, Apr 29, 2019 at 04:17:39PM CEST, [email-masked] 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)?
>> 
>> 
>Correct, this is a suggested debugging solution for a generic problem: 
>enabling the user of a run time memory snapshot for kernel modules (at a 
>given error event). My research shows that other subsystems deal with 
>errors either by panicking (too much) or by debug/log prints (too little).
>This solution is (a) low in maintenance (b) consistent in memory (c) has 
>small performance impact (d) use an existing infra-structure between the 
>kernel module and the user space.

I'm still convinced that dumping kernel memory over devlink health dump
is a good idea :/

>It might be ported to other subsystems using their own user-space vs. 
>kernel tools. Regardless of how the memory output was generated to the 
>user, the parsing script can work on it.

Could you share the script? How is it going to be distributed?

>
>> 
>>> Which other tools do you mean?
>>>>
>>>>
>>>>>
>>>>> Signed-off-by: Aya Levin <[email-masked]>
>>>>> ---
>>>>> .../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
>>>>>