Re: [PATCH rdma-next 3/3] RDMA/hns: Modify hns RoCE device's name

["Wei Hu (Xavier)" <xavier.huwei@huawei.com>]

On 2018/11/27 1:44, Jason Gunthorpe wrote:
> On Mon, Nov 26, 2018 at 04:34:10PM +0800, Wei Hu (Xavier) wrote:
>>
>> On 2018/11/26 11:13, Jason Gunthorpe wrote:
>>> On Sat, Nov 24, 2018 at 09:01:19PM +0800, Wei Hu (Xavier) wrote:
>>>> On 2018/11/24 4:39, Jason Gunthorpe wrote:
>>>>> On Fri, Nov 23, 2018 at 11:14:25PM +0800, Wei Hu (Xavier) wrote:
>>>>>> This patch modifies the name of hns RoCE device's name in order
>>>>>> to ensure that the name is consistent before and after reset.
>>>>>>
>>>>>> Signed-off-by: Wei Hu (Xavier) <xavier.huwei@huawei.com>
>>>>>>  drivers/infiniband/hw/hns/hns_roce_device.h | 1 +
>>>>>>  drivers/infiniband/hw/hns/hns_roce_hw_v2.c  | 3 +++
>>>>>>  drivers/infiniband/hw/hns/hns_roce_main.c   | 4 +++-
>>>>>>  3 files changed, 7 insertions(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/drivers/infiniband/hw/hns/hns_roce_device.h b/drivers/infiniband/hw/hns/hns_roce_device.h
>>>>>> index 259977b..a8cfe76 100644
>>>>>> +++ b/drivers/infiniband/hw/hns/hns_roce_device.h
>>>>>> @@ -954,6 +954,7 @@ struct hns_roce_dev {
>>>>>>  	struct pci_dev		*pci_dev;
>>>>>>  	struct device		*dev;
>>>>>>  	struct hns_roce_uar     priv_uar;
>>>>>> +	char			name[IB_DEVICE_NAME_MAX];
>>>>>>  	const char		*irq_names[HNS_ROCE_MAX_IRQ_NUM];
>>>>>>  	spinlock_t		sm_lock;
>>>>>>  	spinlock_t		bt_cmd_lock;
>>>>>> diff --git a/drivers/infiniband/hw/hns/hns_roce_hw_v2.c b/drivers/infiniband/hw/hns/hns_roce_hw_v2.c
>>>>>> index 1d639a0..678c7ec 100644
>>>>>> +++ b/drivers/infiniband/hw/hns/hns_roce_hw_v2.c
>>>>>> @@ -6110,6 +6110,9 @@ static int hns_roce_hw_v2_get_cfg(struct hns_roce_dev *hr_dev,
>>>>>>  		hr_dev->irq[i] = pci_irq_vector(handle->pdev,
>>>>>>  						i + handle->rinfo.base_vector);
>>>>>>  
>>>>>> +	snprintf(hr_dev->name, IB_DEVICE_NAME_MAX, "hns%s",
>>>>>> +		 handle->rinfo.netdev->name);
>>>>> Why is this making up its own driver name? How is this avoiding
>>>>> colliding with an existing name?
>>>>>
>>>>> This is very dangerous since we now have device renaming, the driver
>>>>> could fail to load with no recovery.
>>>> Hi, Jason
>>>>        
>>>>     The NIC driver notifies the RoCE driver to perform reset related
>>>> processing by calling the .reset_notify() interface registered by the
>>>> RoCE driver. If the RoCE reset processing fails, .reset_notify()
>>>> returns non-zero, and then hns NIC driver will reschedule the
>>>> reset task again.
>>>>    
>>>>     The current hardware version in hip08 SoC cannot support
>>>> after reset process the application still communicates with the
>>>> resources like QP requested before reset. In RoCE reset process,
>>>> we will release the resources through ib_unregister_device, after
>>>> the hardware reset is completed, driver will re-execute
>>>> ib_register_device.
>>>>    
>>>>     Currently, we find that the ib_device's name after reset
>>>> and the one before reset may be different. We can specify the
>>>> device name to solve this problem.
>>> No, now you just have unsolved races.
>>>
>>> If you want to reset like this then you will need to do some kind of
>>> revision to the IB core code to not loose the name assigned to the
>>> device and not hacks like this.
>> Hi, Jason
>>
>>     In fact, We only specified the name of the ib_device to be generated
>> when
>> calling ib_register_device on the hip08 SoC, and doesn't modify its name
>> during the existence of ib_device.
>>
>>     In this example, if you always use hns_%d when registering, I think that
>> no matter how you modify IB core code, we can't solve this problem. We
>> need to specify the name of the ib_device device when calling
>> ib_register_device, and this name should be unique in the OS.
>>
>>     The NIC and the RoCE hardware engine share the function On the hip08
>> SoC.
>> The NIC driver will execute register_netdev firstly, and then the RoCE
>> driver will
>> execute ib_register_device. In the following statement, where
>> handle->rinfo.netdev->name is the name of the corresponding net_device
>> device,
>> this will ensure the uniqueness of the hnsXXX ib_device's name on the OS.
>>
>>     snprintf(hr_dev->name, IB_DEVICE_NAME_MAX, "hns%s",
>>          handle->rinfo.netdev->name);
> It does not. We support rename in ib_core now, so users can set device
> names to whatever they like and break these naming assumptions.
>
> The only solution I can see is to make a reset function in IB core
> that retains the name but forces all clients to disconnect and
> reconnect.
Hi, Jason
    I got your opinion, we will think about how to deal with it.
    Please pull this patch out of the series.
    Thanks you very much!

    Best Regards
Xavier
> Jason
>
> .
>