netdev - Re: [PATCH v12 11/26] nvme-tcp: Add modparam to control the ULP offload enablement

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Message-ID: <175b859c-0c64-3a52-5467-32e06d5c20c9@nvidia.com>
Date: Wed, 16 Aug 2023 04:05:33 +0300
From: Max Gurtovoy <mgurtovoy@...dia.com>
To: Sagi Grimberg <sagi@...mberg.me>, Aurelien Aptel <aaptel@...dia.com>,
 linux-nvme@...ts.infradead.org, netdev@...r.kernel.org, hch@....de,
 kbusch@...nel.org, axboe@...com, chaitanyak@...dia.com, davem@...emloft.net,
 kuba@...nel.org
Cc: aurelien.aptel@...il.com, smalin@...dia.com, malin1024@...il.com,
 ogerlitz@...dia.com, yorayz@...dia.com, borisp@...dia.com,
 galshalom@...dia.com
Subject: Re: [PATCH v12 11/26] nvme-tcp: Add modparam to control the ULP
 offload enablement



On 09/08/2023 11:03, Sagi Grimberg wrote:
> 
> 
> On 7/12/23 19:14, Aurelien Aptel wrote:
>> Add ulp_offload module parameter to the nvme-tcp module to control
>> ULP offload at the NVMe-TCP layer.
>>
>> Turn ULP offload off be default, regardless of the NIC driver support.
>>
>> Overall, in order to enable ULP offload:
>> - nvme-tcp ulp_offload modparam must be set to 1
>> - netdev->ulp_ddp_caps.active must have ULP_DDP_C_NVME_TCP and/or
>>    ULP_DDP_C_NVME_TCP_DDGST_RX capabilities flag set.
>>
>> Signed-off-by: Yoray Zack <yorayz@...dia.com>
>> Signed-off-by: Shai Malin <smalin@...dia.com>
>> Signed-off-by: Aurelien Aptel <aaptel@...dia.com>
>> ---
>>   drivers/nvme/host/tcp.c | 12 +++++++++++-
>>   1 file changed, 11 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
>> index e68e5da3df76..e560bdf3a023 100644
>> --- a/drivers/nvme/host/tcp.c
>> +++ b/drivers/nvme/host/tcp.c
>> @@ -49,6 +49,16 @@ MODULE_PARM_DESC(tls_handshake_timeout,
>>            "nvme TLS handshake timeout in seconds (default 10)");
>>   #endif
>> +#ifdef CONFIG_ULP_DDP
>> +/* NVMeTCP direct data placement and data digest offload will not
>> + * happen if this parameter false (default), regardless of what the
>> + * underlying netdev capabilities are.
>> + */
>> +static bool ulp_offload;
>> +module_param(ulp_offload, bool, 0644);
>> +MODULE_PARM_DESC(ulp_offload, "Enable or disable NVMeTCP ULP support");
> 
> the name is strange.
> maybe call it ddp_offload?

Agree. ddp_offload is a better fit.

> and in the description spell it as "direct data placement"
> 
>> +#endif
>> +
>>   #ifdef CONFIG_DEBUG_LOCK_ALLOC
>>   /* lockdep can detect a circular dependency of the form
>>    *   sk_lock -> mmap_lock (page fault) -> fs locks -> sk_lock
>> @@ -350,7 +360,7 @@ static bool nvme_tcp_ddp_query_limits(struct 
>> net_device *netdev,
>>   static inline bool is_netdev_ulp_offload_active(struct net_device 
>> *netdev,
>>                           struct nvme_tcp_queue *queue)
>>   {
>> -    if (!netdev || !queue)
>> +    if (!ulp_offload || !netdev || !queue)
>>           return false;
>>       /* If we cannot query the netdev limitations, do not offload */
> 
> This patch should be folded to the control path. No reason for it to
> stand on its own I think.

Agree.