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

Junxian Huang
2024-07-09T07:49:30Z

On 2024/7/9 15:22, Leon Romanovsky wrote:
> 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
>

Okay, I'll drop this patch from this patchset in v2 and fix the cmd_mod issues
in another patchset later.

Thanks,
Junxian

>>
>> 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
>>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>