netdev - Re: [PATCH] qed: Enable RDMA relaxed ordering

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Message-ID: <20210826130630.GD1200268@ziepe.ca>
Date:   Thu, 26 Aug 2021 10:06:30 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Shai Malin <smalin@...vell.com>
Cc:     Leon Romanovsky <leon@...nel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Ariel Elior <aelior@...vell.com>,
        "malin1024@...il.com" <malin1024@...il.com>,
        RDMA mailing list <linux-rdma@...r.kernel.org>
Subject: Re: [PATCH] qed: Enable RDMA relaxed ordering

On Thu, Aug 26, 2021 at 12:05:18PM +0000, Shai Malin wrote:
> On Mon, Aug 23, 2021 at 02:52:21PM +0300, Leon Romanovsky wrote:
> > +RDMA
> > 
> > Jakub, David
> > 
> > Can we please ask that everything directly or indirectly related to RDMA
> > will be sent to linux-rdma@ too?
> 
> In addition to all that was discussed regarding qed_rdma.c 
> and qed_rdma_ops - certainly, everything directly or indirectly 
> related to RDMA will be sent to linux-rdma.
> 
> > 
> > On Sun, Aug 22, 2021 at 09:54:48PM +0300, Shai Malin wrote:
> > > Enable the RoCE and iWARP FW relaxed ordering.
> > >
> > > Signed-off-by: Ariel Elior <aelior@...vell.com>
> > > Signed-off-by: Shai Malin <smalin@...vell.com>
> > >  drivers/net/ethernet/qlogic/qed/qed_rdma.c | 2 ++
> > >  1 file changed, 2 insertions(+)
> > >
> > > diff --git a/drivers/net/ethernet/qlogic/qed/qed_rdma.c
> > b/drivers/net/ethernet/qlogic/qed/qed_rdma.c
> > > index 4f4b79250a2b..496092655f26 100644
> > > +++ b/drivers/net/ethernet/qlogic/qed/qed_rdma.c
> > > @@ -643,6 +643,8 @@ static int qed_rdma_start_fw(struct qed_hwfn
> > *p_hwfn,
> > >  				    cnq_id);
> > >  	}
> > >
> > > +	p_params_header->relaxed_ordering = 1;
> > 
> > Maybe it is only description that needs to be updated, but I would
> > expect to see call to pcie_relaxed_ordering_enabled() before setting
> > relaxed_ordering to always true.
> 
> This change will only allow the FW to support relaxed ordering but it 
> will be enabled only if the device/root-complex/server supports 
> relaxed ordering.
> The pcie_relaxed_ordering_enabled() is not needed in this case.

I'm confused, our RDMA model is not to blanket enable relaxed
ordering, we set out rules that the driver has to follow when a
relaxed ordering TLP can be issued:
 - QP/CQ/etc internal queues - device decision based on correctness
 - Kernel created MRs - always
 - User created MRs - only if IB_ACCESS_RELAXED_ORDERING is set

So what does this flag do, and does it follow this model?

Jason