linux-kernel - Re: [PATCH 6/8] NTB: perf: Fix support for hardware that doesn't have port numbers

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Message-ID: <20180615195030.GA25303@mobilestation>
Date:   Fri, 15 Jun 2018 22:50:30 +0300
From:   Serge Semin <fancer.lancer@...il.com>
To:     Logan Gunthorpe <logang@...tatee.com>
Cc:     linux-kernel@...r.kernel.org, linux-ntb@...glegroups.com,
        Jon Mason <jdmason@...zu.us>,
        Dave Jiang <dave.jiang@...el.com>,
        Allen Hubbe <allenbh@...il.com>,
        Shyam Sundar S K <Shyam-sundar.S-k@....com>,
        Shuah Khan <shuah@...nel.org>
Subject: Re: [PATCH 6/8] NTB: perf: Fix support for hardware that doesn't
 have port numbers

On Fri, Jun 08, 2018 at 06:08:17PM -0600, Logan Gunthorpe <logang@...tatee.com> wrote:
> Legacy drivers do not have port numbers (but is reliably only two ports)
> and was broken by the recent commit that added mult-port support to
> ntb_perf. This is especially important to support the cross link
> topology which is perfectly symmetric and cannot assign unique port
> numbers easily.
> 

Please, see the comment to the patch 3/8. I explained everything there
including the fact, that the Intel/AMD drivers do have unique port numbers
assigned.

Regards,
-Sergey

> Hardware that returns zero for both the local port and the peer should
> just always use gidx=0 for the only peer.
> 
> Fixes: 5648e56d03fa ("NTB: ntb_perf: Add full multi-port NTB API support")
> Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
> ---
>  drivers/ntb/test/ntb_perf.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/ntb/test/ntb_perf.c b/drivers/ntb/test/ntb_perf.c
> index fe27412ffe91..6285cb8515ac 100644
> --- a/drivers/ntb/test/ntb_perf.c
> +++ b/drivers/ntb/test/ntb_perf.c
> @@ -1417,6 +1417,16 @@ static int perf_init_peers(struct perf_ctx *perf)
>  	if (perf->gidx == -1)
>  		perf->gidx = pidx;
>  
> +	/*
> +	 * Hardware with only two ports may not have unique port
> +	 * numbers. In this case, the gidxs should all be zero.
> +	 */
> +	if (perf->pcnt == 1 &&  ntb_port_number(perf->ntb) == 0 &&
> +	    ntb_peer_port_number(perf->ntb, 0) == 0) {
> +		perf->gidx = 0;
> +		perf->peers[0].gidx = 0;
> +	}
> +
>  	for (pidx = 0; pidx < perf->pcnt; pidx++) {
>  		ret = perf_setup_peer_mw(&perf->peers[pidx]);
>  		if (ret)
> -- 
> 2.11.0
> 
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