linux-kernel - Re: [PATCH net-next v2 7/7] net/smc: manage system EID in SMC stack instead of ISM driver

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Message-ID: <48732f15-64bf-4bb7-8b88-95263a99cf6a@linux.ibm.com>
Date:   Mon, 27 Nov 2023 15:04:05 +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 v2 7/7] net/smc: manage system EID in SMC stack
 instead of ISM driver



On 24.11.23 15:42, 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>
> ---

Yes, this is what I had in mind. Thank you Wen Gu.
[...]

> 
> diff --git a/drivers/s390/net/ism.h b/drivers/s390/net/ism.h
> index 70c5bbd..49ccbd68 100644
> --- a/drivers/s390/net/ism.h
> +++ b/drivers/s390/net/ism.h

Please remove ISM_IDENT_MASK from drivers/s390/net/ism.h
[...]

> --- a/drivers/s390/net/ism_drv.c
> +++ b/drivers/s390/net/ism_drv.c
> @@ -36,6 +36,7 @@
[...]
> -static void ism_create_system_eid(void)
> -{
> -	struct cpuid id;
> -	u16 ident_tail;
> -	char tmp[5];
> -
> -	get_cpu_id(&id);
> -	ident_tail = (u16)(id.ident & ISM_IDENT_MASK);
> -	snprintf(tmp, 5, "%04X", ident_tail);
> -	memcpy(&SYSTEM_EID.serial_number, tmp, 4);
> -	snprintf(tmp, 5, "%04X", id.machine);
> -	memcpy(&SYSTEM_EID.type, tmp, 4);
> -}
> -
[...]
> @@ -560,7 +535,7 @@ static int ism_dev_init(struct ism_dev *ism)
>  
>  	if (!ism_add_vlan_id(ism, ISM_RESERVED_VLANID))
>  		/* hardware is V2 capable */
> -		ism_create_system_eid();
> +		ism_v2_capable = true;
>  

Please assign 'false' in the else path.
This is required here for backwards compatibility. Hardware that only supports v1,
will reject ISM_RESERVED_VLANID.

[...]


> --- a/net/smc/smc_ism.c
> +++ b/net/smc/smc_ism.c
[...]
> @@ -70,6 +91,11 @@ bool smc_ism_is_v2_capable(void)
>  	return smc_ism_v2_capable;
>  }
>  
> +void smc_ism_set_v2_capable(void)
> +{
> +	smc_ism_v2_capable = true;
> +}
> +
>  /* Set a connection using this DMBE. */
>  void smc_ism_set_conn(struct smc_connection *conn)
>  {
> @@ -431,14 +457,8 @@ 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()) {
> -			smc_ism_v2_capable = true;
> -			memcpy(smc_ism_v2_system_eid, system_eid,
> -			       SMC_MAX_EID_LEN);
> -		}
> +		if (smcd->ops->supports_v2())
> +			smc_ism_set_v2_capable();

I don't see the benefit in declaring smc_ism_set_v2_capable() and exporting it in smc_ism.h,
when it is used only once and only here. 
Why don't you just set 
	smc_ism_v2_capable = true;
here?

[...]
> diff --git a/net/smc/smc_ism.h b/net/smc/smc_ism.h
> index 0e5e563..6903cd5 100644
> --- a/net/smc/smc_ism.h
> +++ b/net/smc/smc_ism.h
> @@ -16,6 +16,7 @@
>  #include "smc.h"
>  
>  #define SMC_VIRTUAL_ISM_CHID_MASK	0xFF00
> +#define SMC_ISM_IDENT_MASK		0x00FFFF
>  
[...]
> @@ -45,6 +52,7 @@ int smc_ism_register_dmb(struct smc_link_group *lgr, int buf_size,
>  void smc_ism_get_system_eid(u8 **eid);
>  u16 smc_ism_get_chid(struct smcd_dev *dev);
>  bool smc_ism_is_v2_capable(void);
> +void smc_ism_set_v2_capable(void);
>  int smc_ism_init(void);
>  void smc_ism_exit(void);
>  int smcd_nl_get_device(struct sk_buff *skb, struct netlink_callback *cb);