netdev - Re: [PATCH net-next 0/4] Make SMC-R can work with rxe devices

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Message-ID: <1bb22ebe-3e54-465f-b076-229e999476a7@huawei.com>
Date: Wed, 28 Aug 2024 18:29:48 +0800
From: "liujian (CE)" <liujian56@...wei.com>
To: Jan Karcher <jaka@...ux.ibm.com>, <dust.li@...ux.alibaba.com>,
	<linux-rdma@...r.kernel.org>, <linux-s390@...r.kernel.org>,
	<netdev@...r.kernel.org>
CC: <jgg@...pe.ca>, <leon@...nel.org>, <zyjzyj2000@...il.com>,
	<wenjia@...ux.ibm.com>, <alibuda@...ux.alibaba.com>,
	<tonylu@...ux.alibaba.com>, <guwen@...ux.alibaba.com>, <davem@...emloft.net>,
	<edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>
Subject: Re: [PATCH net-next 0/4] Make SMC-R can work with rxe devices



在 2024/8/27 3:04, Jan Karcher 写道:
> 
> 
> On 24/08/2024 12:04, liujian (CE) wrote:
>>
>>
>> 在 2024/8/21 9:03, Dust Li 写道:
>>> On 2024-08-20 15:16:57, Jan Karcher wrote:
>>>>
>>>>
>>>> On 09/08/2024 10:31, Liu Jian wrote:
>>>>> Make SMC-R can work with rxe devices. This allows us to easily test 
>>>>> and
>>>>> learn the SMC-R protocol without relying on a physical RoCE NIC.
>>>>
>>>> Hi Liu,
>>>>
>>>> sorry for taking quite some time to answer.
>>>>
>>>> Looking into this i cannot accept this series at the given point of 
>>>> time.
>>>>
>>>> FWIU, RXE is mainly for testing and development and i agree that it 
>>>> would be
>>>> a nice thing to have for SMC-R.
>>>> The problem is that there is no clean layer for different RoCE devices
>>>> currently. Adding RXE to it works but isn't clean.
>>>
>>> Hi jan,
>>>
>>>> Also we have no way to do a "test" build which would have such a device
>>>> supported and a "prod" build which would not support it.
>>>  > I don't quite understand what you mean here, Maybe I missed 
>>> something ?
>>> IIUC, we can control whether to use RXE by simpling insmod or rmmod 
>>> rdma_rxe.ko
> 
> Hi,
> 
> Yes that enables RXE in general, but not the use of RXE in SMC.
> >>>
>> Yes, in the "prod" environment, we can completely turn off 
>> CONFIG_RDMA_RXE.
> 
> Same as above + this is a compile time switch that is enabled for 
> distros like rh. Simply disabling it won't work here.
> 
Got it, I misunderstood what you meant above. Thank you.
>>
>>> I believe having RXE support is beneficial for testing, especially in
>>> simple physical networking setups where many corner cases are unlikely
>>> to occur. By using RXE, we can easily configure unusual scenarios with
>>> the existing iptables/netfilter infrastructure to simulate real-world
>>> situations, such as packet dropping or network retransmission. This
>>> approach can be advantageous for finding hidden bugs.
>>>
>> Yes, one of my main original intentions was to make testing smc-r 
>> easier. This change is relatively simple, mainly patch2 and patch4, 
>> and there are no logical changes.
> 
> I agree with you. It would be beneficial for testing.
> This is not a never, this is a not right now.
> 
> If you want to push this forward as something you need now, feel free to 
> encapsulate it and introduce a vendor specific experimental option as 
> defined in the v2.1 protocol version [1] for it. This would be 
> compromise for me at the current time.
> 
Got it, thanks.
> Thanks
> - Jan
> 
> [1] 
> https://www.ibm.com/support/pages/system/files/inline-files/IBM%20Shared%20Memory%20Communications%20Version%202.1%20Emulated-ISM_0.pdf
> >>> Best regards,
>>> Dust
>>>
>>>
>>>>
>>>> Please give us time to investigate how to solve this in a neat way 
>>>> without
>>>> building up to much technical debt.
>>>>
>>>> Thanks for your contribution and making us aware of this area of 
>>>> improvment.
>>>> - Jan
>>>>
>>>>>
>>>>> Liu Jian (4):
>>>>>     rdma/device: export ib_device_get_netdev()
>>>>>     net/smc: use ib_device_get_netdev() helper to get netdev info
>>>>>     net/smc: fix one NULL pointer dereference in 
>>>>> smc_ib_is_sg_need_sync()
>>>>>     RDMA/rxe: Set queue pair cur_qp_state when being queried
>>>>>
>>>>>    drivers/infiniband/core/core_priv.h   |  3 ---
>>>>>    drivers/infiniband/core/device.c      |  1 +
>>>>>    drivers/infiniband/sw/rxe/rxe_verbs.c |  2 ++
>>>>>    include/rdma/ib_verbs.h               |  2 ++
>>>>>    net/smc/smc_ib.c                      | 10 +++++-----
>>>>>    net/smc/smc_pnet.c                    |  6 +-----
>>>>>    6 files changed, 11 insertions(+), 13 deletions(-)
>>>>>