linux-kernel - Re: [PATCH net-next v3 5/7] net/smc: compatible with 128-bits extend GID of virtual ISM device

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Message-ID: <edb7dc54-a7f9-4356-a2a4-905b5f48b1f0@linux.ibm.com>
Date:   Tue, 5 Dec 2023 10:51:28 +0100
From:   Alexandra Winter <wintera@...ux.ibm.com>
To:     Wen Gu <guwen@...ux.alibaba.com>, wenjia@...ux.ibm.com,
        hca@...ux.ibm.com, gor@...ux.ibm.com, agordeev@...ux.ibm.com,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, kgraul@...ux.ibm.com, jaka@...ux.ibm.com
Cc:     borntraeger@...ux.ibm.com, svens@...ux.ibm.com,
        alibuda@...ux.alibaba.com, tonylu@...ux.alibaba.com,
        raspl@...ux.ibm.com, schnelle@...ux.ibm.com,
        linux-s390@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v3 5/7] net/smc: compatible with 128-bits extend
 GID of virtual ISM device



On 04.12.23 13:24, Wen Gu wrote:
> Thank you very much for review. See below.
> 
> On 2023/12/2 00:30, Alexandra Winter wrote:
>>
>>
>> On 30.11.23 12:28, Wen Gu wrote:
>> [...]
>>> diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
>>> index 766a1f1..d1e18bf 100644
>>> --- a/net/smc/af_smc.c
>>> +++ b/net/smc/af_smc.c
>> [...]
>>> @@ -1048,7 +1048,8 @@ static int smc_find_ism_v2_device_clnt(struct smc_sock *smc,
>>>   {
>>>       int rc = SMC_CLC_DECL_NOSMCDDEV;
>>>       struct smcd_dev *smcd;
>>> -    int i = 1;
>>> +    int i = 1, entry = 1;
>>> +    bool is_virtual;
>>>       u16 chid;
>>>         if (smcd_indicated(ini->smc_type_v1))
>>> @@ -1060,14 +1061,23 @@ static int smc_find_ism_v2_device_clnt(struct smc_sock *smc,
>>>           chid = smc_ism_get_chid(smcd);
>>>           if (!smc_find_ism_v2_is_unique_chid(chid, ini, i))
>>>               continue;
>>> +        is_virtual = __smc_ism_is_virtual(chid);
>>>           if (!smc_pnet_is_pnetid_set(smcd->pnetid) ||
>>>               smc_pnet_is_ndev_pnetid(sock_net(&smc->sk), smcd->pnetid)) {
>>> +            if (is_virtual && entry == SMC_MAX_ISM_DEVS)
>>> +                /* only one GID-CHID entry left in CLC Proposal SMC-Dv2
>>> +                 * extension. but a virtual ISM device's GID takes two
>>> +                 * entries. So give up it and try the next potential ISM
>>> +                 * device.
>>> +                 */
>>
>> It is really importatnt to note that virtual ISMs take 2 entries.
>> But it is still hard to understand this piece of code. e.g. I was wondering for a while,
>> why you mention CLC here...
>> Maybe it would be easier to understand this, if you rename SMC_MAX_ISM_DEVS to something else?
>> Something like SMCD_MAX_V2_GID_ENTRIES?
>>
> 
> I agree.
> 
> But I perfer to define a new macro to represent the max ISMv2 entries in CLC proposal message,
> e.g. SMCD_CLC_MAX_V2_GID_ENTRIES, and keep using SMC_MAX_ISM_DEVS to represent the max devices
> that can be proposed. Both semantics are required in the code, such as:
> 
> ini->ism_dev[SMC_MAX_ISM_DEVS]        | smcd_v2_ext->gidchid[SMCD_CLC_MAX_V2_GID_ENTRIES]
> -------------------------------------------------------------------------------------------
> [1:virtual_ISM_1]                     | [1:virtual_ISM_1 GID]
>                                       | [2:virtual_ISM_1 extension GID]
> [2:ISM_2]                             | [3:ISM_2 GID/CHID]
> [3:ISM_3]                             | [4:ISM_3 GID/CHID]
> 
> And SMC_MAX_ISM_DEVS is required no more than SMCD_CLC_MAX_V2_GID_ENTRIES.

I agree, this is even better.