linux-kernel - Re: [PATCH rdma-next 1/1] RDMA/mana

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Message-ID:
 <DU8PR83MB0975E65E87B49534950E9447B499A@DU8PR83MB0975.EURPRD83.prod.outlook.com>
Date: Thu, 5 Feb 2026 12:03:18 +0000
From: Konstantin Taranov <kotaranov@...rosoft.com>
To: Leon Romanovsky <leon@...nel.org>, Jason Gunthorpe <jgg@...pe.ca>
CC: Konstantin Taranov <kotaranov@...ux.microsoft.com>, Shiraz Saleem
	<shirazsaleem@...rosoft.com>, Long Li <longli@...rosoft.com>,
	"linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH rdma-next 1/1] RDMA/mana_ib: return PD number to the user

> 
> On Wed, Feb 04, 2026 at 10:28:27AM -0400, Jason Gunthorpe wrote:
> > On Wed, Feb 04, 2026 at 05:58:13AM -0800, Konstantin Taranov wrote:
> > > From: Konstantin Taranov <kotaranov@...rosoft.com>
> > >
> > > Implement returning to userspace applications PDNs of created PDs.
> > > Allow users to request short PDNs which are 16 bits.
> >
> > Why does userspace ever need to see a PDN? Please justify that in the
> > commit message
> 
> Probably for the debug and we have restrack for it.
> 

Sure, I will add the explanation in v2. Overall, it is for applications working on top of the rdma-core (e.g., mana DPDK).
The use-case is similar to what mlx4 and mthca have for address vectors in rdma-core for isolation.
As the whole process of working with WQs and CQs is implemented in that applications (e.g., mana DPDK), they need to know
PDN to build a correct request. What is more, the HW folks put a limit of 16 bits to the PDN field, requiring a flag to ensure
that we get a PDN that fits into the field.

I hope that it justifies the change as most ib providers have pdn in the user-space.

- Konstantin

> Thanks
> 
> >
> > Jason