netdev - RE: [PATCH V2 mlx5-next 09/11] net/mlx5: Eswitch, enable RoCE loopback traffic

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Message-ID: <VI1PR0501MB22719EBFAF3F1BBEF81D7823D1390@VI1PR0501MB2271.eurprd05.prod.outlook.com>
Date:   Mon, 29 Apr 2019 22:34:51 +0000
From:   Parav Pandit <parav@...lanox.com>
To:     Mark Bloch <markb@...lanox.com>,
        Leon Romanovsky <leonro@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>
CC:     Jason Gunthorpe <jgg@...lanox.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        Maor Gottlieb <maorg@...lanox.com>
Subject: RE: [PATCH V2 mlx5-next 09/11] net/mlx5: Eswitch, enable RoCE
 loopback traffic

Hi Mark,

> -----Original Message-----
> From: Mark Bloch
> Sent: Monday, April 29, 2019 5:31 PM
> To: Parav Pandit <parav@...lanox.com>; Leon Romanovsky
> <leonro@...lanox.com>; Saeed Mahameed <saeedm@...lanox.com>
> Cc: Jason Gunthorpe <jgg@...lanox.com>; netdev@...r.kernel.org; linux-
> rdma@...r.kernel.org; Maor Gottlieb <maorg@...lanox.com>
> Subject: Re: [PATCH V2 mlx5-next 09/11] net/mlx5: Eswitch, enable RoCE
> loopback traffic
> 
> 
> 
> On 4/29/19 11:45 AM, Parav Pandit wrote:
> >
> >
> >> -----Original Message-----
> >> From: netdev-owner@...r.kernel.org <netdev-owner@...r.kernel.org>
> On
> >> Behalf Of Leon Romanovsky
> >> Sent: Monday, April 29, 2019 1:41 PM
> >> To: Saeed Mahameed <saeedm@...lanox.com>
> >> Cc: Jason Gunthorpe <jgg@...lanox.com>; netdev@...r.kernel.org;
> >> linux- rdma@...r.kernel.org; Maor Gottlieb <maorg@...lanox.com>;
> Mark
> >> Bloch <markb@...lanox.com>
> >> Subject: Re: [PATCH V2 mlx5-next 09/11] net/mlx5: Eswitch, enable
> >> RoCE loopback traffic
> >>
> >> On Mon, Apr 29, 2019 at 06:14:16PM +0000, Saeed Mahameed wrote:
> >>> From: Maor Gottlieb <maorg@...lanox.com>
> >>>
> >>> When in switchdev mode, we would like to treat loopback RoCE traffic
> >>> (on eswitch manager) as RDMA and not as regular Ethernet traffic In
> >>> order to enable it we add flow steering rule that forward RoCE
> >>> loopback traffic to the HW RoCE filter (by adding allow rule).
> >>> In addition we add RoCE address in GID index 0, which will be set in
> >>> the RoCE loopback packet.
> >>>
> > I likely don't understand nor I reviewed the patches.
> > Part that I don't understand is GID index 0 for RoCE.
> > RoCE traffic runs over all the GID entries and for all practical purposes from
> non_zero index.
> > How will it work?
> 
> Currently in switchdev mode we only support RAW Ethernet QP and no RoCE
> capabilities are reported to ib_core.
> Which means no GIDs are inserted to the HW's GID table and RoCE isn't
> enabled on the vport.
> 
> However, there are cases where an internal RC QP might be needed, and for
> that we need a GID.
> The patches from Maor make sure a GID entry at index 0 is valid (and we do
> that only in switchdev mode), and with steering we make sure such traffic is
> only used for loopback purposes.

Got it. Thanks for the detailed description. Its clear to me now.