Re: [PATCH rdma-next 10/11] RDMA/erdma: Add the ABI definitions

[Cheng Xu <chengyou@linux.alibaba.com>]

On 12/25/21 2:19 AM, Leon Romanovsky wrote:
> On Fri, Dec 24, 2021 at 03:12:35PM +0800, Cheng Xu wrote:
>>
>>
>> On 12/24/21 6:55 AM, Yanjun Zhu wrote:
>>> 在 2021/12/24 2:45, Leon Romanovsky 写道:
>>>> On Thu, Dec 23, 2021 at 11:46:03PM +0800, Yanjun Zhu wrote:
>>>>> 在 2021/12/21 10:48, Cheng Xu 写道:
>>>>>> Signed-off-by: Cheng Xu <chengyou@linux.alibaba.com>
>>>>>> ---
>>>>>>     include/uapi/rdma/erdma-abi.h | 49
>>>>>> +++++++++++++++++++++++++++++++++++
>>>>>>     1 file changed, 49 insertions(+)
>>>>>>     create mode 100644 include/uapi/rdma/erdma-abi.h
>>>>>>
>>>>>> diff --git a/include/uapi/rdma/erdma-abi.h
>>>>>> b/include/uapi/rdma/erdma-abi.h
>>>>>> new file mode 100644
>>>>>> index 000000000000..6bcba10c1e41
>>>>>> --- /dev/null
>>>>>> +++ b/include/uapi/rdma/erdma-abi.h
>>>>>> @@ -0,0 +1,49 @@
>>>>>> +/* SPDX-License-Identifier: ((GPL-2.0 WITH
>>>>>> Linux-syscall-note) OR Linux-OpenIB) */
>>>>>> +/*
>>>>>> + * Copyright (c) 2020-2021, Alibaba Group.
>>>>>> + */
>>>>>> +
>>>>>> +#ifndef __ERDMA_USER_H__
>>>>>> +#define __ERDMA_USER_H__
>>>>>> +
>>>>>> +#include <linux/types.h>
>>>>>> +
>>>>>> +#define ERDMA_ABI_VERSION       1
>>>>>
>>>>> ERDMA_ABI_VERSION should be 2？
>>>>
>>>> Why?
>>>>
>>>> This field is for rdma-core and we don't have erdma provider in that
>>>> library yet. It always starts from 1 for new drivers.
>>> Please check this link:
>>> http://mail.spinics.net/lists/linux-rdma/msg63012.html
>>>
>>> Jason mentioned in this link:
>>>
>>> "
>>> /*
>>>    * For 64 bit machines ABI version 1 and 2 are the same. Otherwise 32
>>>    * bit machines require ABI version 2 which guarentees the user and
>>>    * kernel use the same ABI.
>>>    */
>>> "
>>>
>>> Zhu Yanjun
>>
>> Even though I do not understand the reason, but as mentioned above, I think
>> ERDMA_ABI_VERSION = 1 is fine, because ERDMA can only work in 64bit
>> machines.
> 
> Jason's comment came after we discovered that many of our API structures had
> problematic layout and weren't aligned to 64bits. This caused to issues when
> the 32bits software tried to use 64bit kernel.
> 
> So we didn't have many choices but bump ABI versions for broken drivers
> and RXE was one of them.
> 
> You are proposing new driver, it should start from 1.

Thanks for your explanation.

Thanks,
Cheng Xu

> Thanks