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

["Niklas Söderlund" <niklas.soderlund@corigine.com>]

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?

> 
> 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-should-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