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

Leon Romanovsky
2024-07-09T07:22:31Z

On Tue, Jul 09, 2024 at 02:21:31PM +0800, Junxian Huang wrote:
>
>
> On 2024/7/8 19:16, Leon Romanovsky wrote:
> > On Mon, Jul 08, 2024 at 05:30:58PM +0800, Junxian Huang wrote:
> >>
> >>
> >> On 2024/7/8 16:59, Leon Romanovsky wrote:
> >>> 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?
> >>
> >> The changing of cmd_mod is during the initialization of a device. The call
> >> of hns_roce_v2_reset_notify_cmd() is during reset. As I said previously,
> >> the hns3 NIC driver ensures that there will be no concurrency between
> >> initialization and reset, and therefore hns_roce_v2_reset_notify_cmd() won't
> >> be called in the middle of changing cmd_mod.
> >>
> >>> 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.
> >>>
> >>
> >> But event mode relies on the allocated resource. If the allocation fails and
> >> we don't switch to polling mode, the driver won't work any more. Are you suggesting
> >> we should return an error and fail the initialization in this case?
> >
> > Yes, please.
>
> The reason of switching cmd_mod is that we try to keep the driver available,
> even if the allocation of event mode resources fails. We don't consider this
> as a critical error that should lead to an initialization failure. The driver
> can still post mailbox and provide normal functionality in this case.

Driver that failed to allocate memory in the middle of initialization
can't be considered as "normal".

>
> Our discussion seems to have strayed a bit away？This patch doesn't involve
> polling mode.

As long as patch has this line "if (!hr_dev->cmd_mod)", this discussion
is related to polling mode.

Thanks

>
> Junxian
>
> >
> > Thanks
> >
> >>
> >> Junxian
> >>
> >>> 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
> >>>>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>
> >>>>
> >>>
> >>
> >