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

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Message-ID: <5BFBB002.8020703@huawei.com>
Date:   Mon, 26 Nov 2018 16:34:10 +0800
From:   "Wei Hu (Xavier)" <xavier.huwei@...wei.com>
To:     Jason Gunthorpe <jgg@...pe.ca>
CC:     <dledford@...hat.com>, <linux-rdma@...r.kernel.org>,
        <lijun_nudt@....com>, <oulijun@...wei.com>,
        <charles.chenxin@...wei.com>, <liuyixian@...wei.com>,
        <zhangxiping3@...wei.com>, <linuxarm@...wei.com>,
        <linux-kernel@...r.kernel.org>, <xavier_huwei@....com>
Subject: Re: [PATCH rdma-next 3/3] RDMA/hns: Modify hns RoCE device's name



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@...wei.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);

    Best Regards
Xavier
> Jason
>
> .
>