netdev - Re: [PATCH net-next v3 7/7] net/smc: manage system EID in SMC stack instead of ISM driver

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Date: Mon, 4 Dec 2023 20:36:07 +0800
From: Wen Gu <guwen@...ux.alibaba.com>
To: Alexandra Winter <wintera@...ux.ibm.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 7/7] net/smc: manage system EID in SMC stack
 instead of ISM driver


On 2023/12/1 19:18, Alexandra Winter wrote:
> 
> 
> On 30.11.23 12:28, Wen Gu wrote:
>> The System EID (SEID) is an internal EID that is used by the SMCv2
>> software stack that has a predefined and constant value representing
>> the s390 physical machine that the OS is executing on. So it should
>> be managed by SMC stack instead of ISM driver and be consistent for
>> all ISMv2 device (including virtual ISM devices) on s390 architecture.
>>
>> Suggested-by: Alexandra Winter <wintera@...ux.ibm.com>
>> Signed-off-by: Wen Gu <guwen@...ux.alibaba.com>
>> ---
> 
> Reviewed-by: Alexandra Winter <wintera@...ux.ibm.com>
> 
> 
> [...]
>> diff --git a/net/smc/smc_ism.c b/net/smc/smc_ism.c
>> index a33f861..ac88de2 100644
>> --- a/net/smc/smc_ism.c
>> +++ b/net/smc/smc_ism.c
> [...]
>> @@ -431,14 +452,8 @@ static void smcd_register_dev(struct ism_dev *ism)
>>   
>>   	mutex_lock(&smcd_dev_list.mutex);
>>   	if (list_empty(&smcd_dev_list.list)) {
>> -		u8 *system_eid = NULL;
>> -
>> -		system_eid = smcd->ops->get_system_eid();
>> -		if (smcd->ops->supports_v2()) {
>> +		if (smcd->ops->supports_v2())
>>   			smc_ism_v2_capable = true;
>> -			memcpy(smc_ism_v2_system_eid, system_eid,
>> -			       SMC_MAX_EID_LEN);
>> -		}
>>   	}
> 
> Just a comment:
> Here we only check the first smcd device to determine whether we support v2.
> Which is ok, for today's platform firmware ISM devices, as they are always the same version.
> 
> When you add virtual ISM devices (loopback-ism, virtio-ism) then this needs to be changed.
> IMO the logic then needs to be "if all smcd devices support v2,
> then smc_ism_v2_capable = true;
> else smc_ism_v2_capable = false;"
> 

Thank you. I will change this in the loopback-ism patch set.

But I am wondering if loopback-ism coexists with s390 ISMv1, why smc_ism_v2_capable shouldn't be set?
Is it because the SEID generated in this way is not correct if the s390 ISMv2 does not exist?

> I don't know if you would like to change that now in this patch, or later when
> you add when you add the support for loopback.
> 
>