Re: [PATCH] net/nfp: support 48-bit DMA address for firmware with NFDk

[Ferruh Yigit <ferruh.yigit@amd.com>]

On 2/16/2023 11:11 AM, Nole Zhang wrote:
> 
> 
>> -----Original Message-----
>> From: Ferruh Yigit <ferruh.yigit@amd.com>
>> Sent: Thursday, February 16, 2023 7:00 PM
>> To: Chaoyong He <chaoyong.he@corigine.com>; Niklas Soderlund
>> <niklas.soderlund@corigine.com>; Kevin Traynor <ktraynor@redhat.com>
>> Cc: Xueming(Steven) Li <xuemingl@nvidia.com>; dev@dpdk.org; Luca
>> Boccassi <bluca@debian.org>; oss-drivers <oss-drivers@corigine.com>; Nole
>> Zhang <peng.zhang@corigine.com>; Kevin Liu <jin.liu@corigine.com>;
>> stable@dpdk.org
>> Subject: Re: [PATCH] net/nfp: support 48-bit DMA address for firmware with
>> NFDk
>>
>> On 2/16/2023 10:41 AM, Chaoyong He wrote:
>>>
>>>
>>>> -----Original Message-----
>>>> From: Niklas Soderlund <niklas.soderlund@corigine.com>
>>>> Sent: Thursday, February 16, 2023 6:37 PM
>>>> To: Kevin Traynor <ktraynor@redhat.com>
>>>> Cc: Ferruh Yigit <ferruh.yigit@amd.com>; Xueming(Steven) Li
>>>> <xuemingl@nvidia.com>; Chaoyong He <chaoyong.he@corigine.com>;
>>>> dev@dpdk.org; Luca Boccassi <bluca@debian.org>; oss-drivers <oss-
>>>> drivers@corigine.com>; Nole Zhang <peng.zhang@corigine.com>; Kevin
>>>> Liu <jin.liu@corigine.com>; stable@dpdk.org
>>>> Subject: Re: [PATCH] net/nfp: support 48-bit DMA address for firmware
>>>> with NFDk
>>>>
>>>> Hi Kevin,
>>>>
>>>> Thanks for your input.
>>>>
>>>> On 2023-02-16 10:28:34 +0000, Kevin Traynor wrote:
>>>>> On 15/02/2023 18:28, Ferruh Yigit wrote:
>>>>>> On 2/15/2023 5:47 PM, Niklas Söderlund wrote:
>>>>>>> Hi Ferruh,
>>>>>>>
>>>>>>> Thanks for your continues effort in dealing with NFP patches.
>>>>>>>
>>>>>>> On 2023-02-15 13:42:01 +0000, Ferruh Yigit wrote:
>>>>>>>> On 2/8/2023 9:15 AM, Chaoyong He wrote:
>>>>>>>>> From: Peng Zhang <peng.zhang@corigine.com>
>>>>>>>>>
>>>>>>>>> 48-bit DMA address is supported in the firmware with NFDk, so
>>>>>>>>> enable this feature in PMD now. But the firmware with NFD3 still
>>>>>>>>> just support 40-bit DMA address.
>>>>>>>>>
>>>>>>>>> RX free list descriptor, used by both NFD3 and NFDk, is also
>>>>>>>>> modified to support 48-bit DMA address. That's OK because the
>>>>>>>>> top bits is always set to 0 when assigned with 40-bit DMA address.
>>>>>>>>>
>>>>>>>>> Fixes: c73dced48c8c ("net/nfp: add NFDk Tx")
>>>>>>>>> Cc: jin.liu@corigine.com
>>>>>>>>> Cc: stable@dpdk.org
>>>>>>>>>
>>>>>>>>
>>>>>>>> Why a backport is requested? As far as I understand this is not
>>>>>>>> fixing anything but extending device capability. Is this a fix?
>>>>>>>
>>>>>>> I agree this is a bit of a grey zone. We reasoned this was a fix
>>>>>>> as we should have done this from the start in the commit that
>>>>>>> added support for NFDk. Are you OK moving forward with this as a
>>>>>>> fix or would you prefer we resubmit without the request to backport?
>>>>>>>
>>>>>>
>>>>>> I am not sure, is this change have any potential to change behavior
>>>>>> for existing users?
>>>>>> Like if one of your user is using 22.11.1 release, and if this
>>>>>> patch backported to next LTS version, 22.11.2, will user notice any
>> difference?
>>>>>>
>>>>>>
>>>>>> @Luca, @Kevin, what is your comment as LTS maintainers?
>>>>>>
>>>>>
>>>>> A bit difficult to know. If NFDk is not practicably usable without
>>>>> it, then it could be considered a fix. If it's just extending to add
>>>>> nice-to-have functionality then probably it is not a fix.
>>>>
>>>> I think we can treat this as a nice-to-have and not something that
>>>> makes NFDk unusable. As stated above, we marked this as a Fix as we
>>>> *really* should have done this in the commit which added NFDk support.
>>>>
>>>> @Ferruh, would you prefer we send a v2 or will you drop the Fixes and
>>>> CC tags when/if applying?
>>>>
>>>
>>> Actually, the DPDK app using the nfp card with a firmware of NFDk will
>> coredump without this patch.
>>> And that's the directly reason we consider backport this patch.
>>>
>>
>> It has been long since NFDk FW support added, how a crash missed until this
>> point, is it crashing in a edge case or something?
>>
> Yes, this occur in the server with CPU FT-2000/64, it has 2 PCIE1 x8 and 1 PCIE0 x16,
> Pcie x8 can only support 48 bit, but the pcie16 can support 40bit.

OK, can you please send a new version of the patch updating patch title
and commit log to highlight that patch is fixing a crash.

It can be helpful to detail the reason of crash in commit log.

>>>>>
>>>>> It would need to ensure that it is tested on 22.11 branch and there
>>>>> are no regressions. It is only relevant to DPDK 22.11 LTS so Cc
>>>>> Xueming who will ultimately decide.
>>>>>
>>>>> A guide below on some things to consider for this type of backport is
>> here:
>>>>> http://doc.dpdk.org/guides/contributing/stable.html#what-changes-sho
>>>>> ul
>>>>> d-be-backported
>>>>>
>>>>>>>>
>>>>>>>>> Signed-off-by: Peng Zhang <peng.zhang@corigine.com>
>>>>>>>>> Reviewed-by: Chaoyong He <chaoyong.he@corigine.com>
>>>>>>>>> Reviewed-by: Niklas Söderlund <niklas.soderlund@corigine.com>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>> --
>>>> Kind Regards,
>>>> Niklas Söderlund
>