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Date:   Thu, 16 May 2019 08:49:54 +0000
From:   Aya Levin <ayal@...lanox.com>
To:     Jiri Pirko <jiri@...nulli.us>
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



On 5/14/2019 3:07 PM, Jiri Pirko wrote:
> Sun, May 12, 2019 at 10:37:35AM CEST, ayal@...lanox.com wrote:
>>
>>
>> On 5/9/2019 11:23 AM, Jiri Pirko wrote:
>>> 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)?
>>>
>>>
>> 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?
I thought that the script should be in a available on Mellanox website. 
The script is still pending review but I will be happy to share it when 
its ready.
> 
> 
>>
>>>
>>>> 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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