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

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Date:   Mon, 26 Nov 2018 10:44:02 -0700
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     "Wei Hu (Xavier)" <xavier.huwei@...wei.com>
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 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@...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);

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.

Jason