Re: [PATCH for-rc 2/9] RDMA/hns: Fix a long wait for cmdq event during reset

[Leon Romanovsky <leon@kernel.org>]

On Mon, Jul 08, 2024 at 04:45:34PM +0800, Junxian Huang wrote:
> 
> 
> On 2024/7/8 16:27, Leon Romanovsky wrote:
> > On Mon, Jul 08, 2024 at 03:46:26PM +0800, Junxian Huang wrote:
> >>
> >>
> >> On 2024/7/8 15:33, Leon Romanovsky wrote:
> >>> On Mon, Jul 08, 2024 at 02:50:50PM +0800, Junxian Huang wrote:
> >>>>
> >>>>
> >>>> On 2024/7/8 13:38, Leon Romanovsky wrote:
> >>>>> On Mon, Jul 08, 2024 at 10:29:54AM +0800, Junxian Huang wrote:
> >>>>>>
> >>>>>>
> >>>>>> On 2024/7/7 16:30, Leon Romanovsky wrote:
> >>>>>>> On Fri, Jul 05, 2024 at 04:59:30PM +0800, Junxian Huang wrote:
> >>>>>>>> From: wenglianfa <wenglianfa@huawei.com>
> >>>>>>>>
> >>>>>>>> During reset, cmdq events won't be reported, leading to a long and
> >>>>>>>> unnecessary wait. Notify all the cmdqs to stop waiting at the beginning
> >>>>>>>> of reset.
> >>>>>>>>
> >>>>>>>> Fixes: 9a4435375cd1 ("IB/hns: Add driver files for hns RoCE driver")
> >>>>>>>> Signed-off-by: wenglianfa <wenglianfa@huawei.com>
> >>>>>>>> Signed-off-by: Junxian Huang <huangjunxian6@hisilicon.com>
> >>>>>>>> ---
> >>>>>>>>  drivers/infiniband/hw/hns/hns_roce_hw_v2.c | 18 ++++++++++++++++++
> >>>>>>>>  1 file changed, 18 insertions(+)
> >>>>>>>>
> >>>>>>>> diff --git a/drivers/infiniband/hw/hns/hns_roce_hw_v2.c b/drivers/infiniband/hw/hns/hns_roce_hw_v2.c
> >>>>>>>> index a5d746a5cc68..ff135df1a761 100644
> >>>>>>>> --- a/drivers/infiniband/hw/hns/hns_roce_hw_v2.c
> >>>>>>>> +++ b/drivers/infiniband/hw/hns/hns_roce_hw_v2.c
> >>>>>>>> @@ -6977,6 +6977,21 @@ static void hns_roce_hw_v2_uninit_instance(struct hnae3_handle *handle,
> >>>>>>>>  
> >>>>>>>>  	handle->rinfo.instance_state = HNS_ROCE_STATE_NON_INIT;
> >>>>>>>>  }
> >>>>>>>> +
> >>>>>>>> +static void hns_roce_v2_reset_notify_cmd(struct hns_roce_dev *hr_dev)
> >>>>>>>> +{
> >>>>>>>> +	struct hns_roce_cmdq *hr_cmd = &hr_dev->cmd;
> >>>>>>>> +	int i;
> >>>>>>>> +
> >>>>>>>> +	if (!hr_dev->cmd_mod)
> >>>>>>>
> >>>>>>> What prevents cmd_mod from being changed?
> >>>>>>>
> >>>>>>
> >>>>>> It's set when the device is being initialized, and won't be changed after that.
> >>>>>
> >>>>> This is exactly the point, you are assuming that the device is already
> >>>>> ininitialized or not initialized at all. What prevents hns_roce_v2_reset_notify_cmd()
> >>>>> from being called in the middle of initialization?
> >>>>>
> >>>>> Thanks
> >>>>>
> >>>>
> >>>> This is ensured by hns3 NIC driver.
> >>>>
> >>>> Initialization and reset of hns RoCE are both called by hns3. It will check the state
> >>>> of RoCE device (see line 3798), and notify RoCE device to reset (hns_roce_v2_reset_notify_cmd()
> >>>> is called) only if the RoCE device has been already initialized:
> >>>
> >>> So why do you have "if (!hr_dev->cmd_mod)" check in the code?
> >>>
> >>> Thanks
> >>>
> >>
> >> cmd_mod indicates the mode of cmdq (0: poll mode, 1: event mode).
> >> This patch only affects event mode because HW won't report events during reset.
> > 
> > You set cmd_mod to 1 in hns_roce_hw_v2_init_instance() without any
> > condition, I don't see when hns v2 IB device is created and continue
> > to operate in polling mode. 
> > 
> > Thanks
> >
> 
> Event mode is the default. In hns_roce_cmd_use_events(), if kcalloc() fails
> then it'll be set to polling mode instead.

1. Awesome, and we are returning back to the question. What prevents
   hns_roce_v2_reset_notify_cmd() from being called in the middle of
   changing cmd_mod from 1 to 0 and from 0 to 1?
2. This cmd_mode swtich from 1 to 0 should be removed. Failure to
   allocate memory is not a reason to switch to polling mode. The reason
   can be HW limitation, but not OS limitation.

Thanks

> 
> Junxian
> 
> >>
> >> Junxian
> >>
> >>>>
> >>>>  3791 static int hclge_notify_roce_client(struct hclge_dev *hdev,
> >>>>  3792                                     enum hnae3_reset_notify_type type)
> >>>>  3793 {
> >>>>  3794         struct hnae3_handle *handle = &hdev->vport[0].roce;
> >>>>  3795         struct hnae3_client *client = hdev->roce_client;
> >>>>  3796         int ret;
> >>>>  3797
> >>>>  3798         if (!test_bit(HCLGE_STATE_ROCE_REGISTERED, &hdev->state) || !client)
> >>>>  3799                 return 0;
> >>>>  3800
> >>>>  3801         if (!client->ops->reset_notify)
> >>>>  3802                 return -EOPNOTSUPP;
> >>>>  3803
> >>>>  3804         ret = client->ops->reset_notify(handle, type);
> >>>>  3805         if (ret)
> >>>>  3806                 dev_err(&hdev->pdev->dev, "notify roce client failed %d(%d)",
> >>>>  3807                         type, ret);
> >>>>  3808
> >>>>  3809         return ret;
> >>>>  3810 }
> >>>>
> >>>> And the bit is set (see line 11246) after the initialization has been done (line 11242):
> >>>>
> >>>> 11224 static int hclge_init_roce_client_instance(struct hnae3_ae_dev *ae_dev,
> >>>> 11225                                            struct hclge_vport *vport)
> >>>> 11226 {
> >>>> 11227         struct hclge_dev *hdev = ae_dev->priv;
> >>>> 11228         struct hnae3_client *client;
> >>>> 11229         int rst_cnt;
> >>>> 11230         int ret;
> >>>> 11231
> >>>> 11232         if (!hnae3_dev_roce_supported(hdev) || !hdev->roce_client ||
> >>>> 11233             !hdev->nic_client)
> >>>> 11234                 return 0;
> >>>> 11235
> >>>> 11236         client = hdev->roce_client;
> >>>> 11237         ret = hclge_init_roce_base_info(vport);
> >>>> 11238         if (ret)
> >>>> 11239                 return ret;
> >>>> 11240
> >>>> 11241         rst_cnt = hdev->rst_stats.reset_cnt;
> >>>> 11242         ret = client->ops->init_instance(&vport->roce);
> >>>> 11243         if (ret)
> >>>> 11244                 return ret;
> >>>> 11245
> >>>> 11246         set_bit(HCLGE_STATE_ROCE_REGISTERED, &hdev->state);
> >>>> 11247         if (test_bit(HCLGE_STATE_RST_HANDLING, &hdev->state) ||
> >>>> 11248             rst_cnt != hdev->rst_stats.reset_cnt) {
> >>>> 11249                 ret = -EBUSY;
> >>>> 11250                 goto init_roce_err;
> >>>> 11251         }
> >>>>
> >>>> Junxian
> >>>>
> >>>>>>
> >>>>>> Junxian
> >>>>>>
> >>>>>>>> +		return;
> >>>>>>>> +
> >>>>>>>> +	for (i = 0; i < hr_cmd->max_cmds; i++) {
> >>>>>>>> +		hr_cmd->context[i].result = -EBUSY;
> >>>>>>>> +		complete(&hr_cmd->context[i].done);
> >>>>>>>> +	}
> >>>>>>>> +}
> >>>>>>>> +
> >>>>>>>>  static int hns_roce_hw_v2_reset_notify_down(struct hnae3_handle *handle)
> >>>>>>>>  {
> >>>>>>>>  	struct hns_roce_dev *hr_dev;
> >>>>>>>> @@ -6997,6 +7012,9 @@ static int hns_roce_hw_v2_reset_notify_down(struct hnae3_handle *handle)
> >>>>>>>>  	hr_dev->dis_db = true;
> >>>>>>>>  	hr_dev->state = HNS_ROCE_DEVICE_STATE_RST_DOWN;
> >>>>>>>>  
> >>>>>>>> +	/* Complete the CMDQ event in advance during the reset. */
> >>>>>>>> +	hns_roce_v2_reset_notify_cmd(hr_dev);
> >>>>>>>> +
> >>>>>>>>  	return 0;
> >>>>>>>>  }
> >>>>>>>>  
> >>>>>>>> -- 
> >>>>>>>> 2.33.0
> >>>>>>>>
> >>>>>>
> >>>>
>