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From: "Allen Hubbe" <Allen.Hubbe@dell.com>
References: <20170605200053.6912-1-logang@deltatee.com> <20170605200053.6912-2-logang@deltatee.com>
In-Reply-To: <20170605200053.6912-2-logang@deltatee.com>
Subject: RE: [PATCH] ntb_transport: fix qp count bug
Date: Tue, 6 Jun 2017 09:08:47 -0400
Message-ID: <000201d2dec6$08e211d0$1aa63570$@dell.com>
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To: 'Logan Gunthorpe' <logang@deltatee.com>, linux-ntb@googlegroups.com
Cc: 'Jon Mason' <jdmason@kudzu.us>, 'Dave Jiang' <dave.jiang@intel.com>
List-ID: <linux-ntb.googlegroups.com>

From: Logan Gunthorpe
> In cases where there are more mw's than spads/2-2, the mw count gets
> reduced to match the limitation. ntb_transport also tries to ensure that
> there are fewer qps than mws but uses the full mw count instead of
> the reduced one. When this happens, the math in
> 'ntb_transport_setup_qp_mw' will get confused and result in a kernel
> paging request bug.
> 
> This patch fixes the bug by reducing qp_count to the reduced mw count
> instead of the full mw count.
> 
> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
> Cc: Jon Mason <jdmason@kudzu.us>
> Cc: Dave Jiang <dave.jiang@intel.com>
> Cc: Allen Hubbe <Allen.Hubbe@emc.com>

Acked-by: Allen Hubbe <Allen.Hubbe@dell.com>

> ---
>  drivers/ntb/ntb_transport.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/ntb/ntb_transport.c b/drivers/ntb/ntb_transport.c
> index 02ca45fdd892..0a778d2cab94 100644
> --- a/drivers/ntb/ntb_transport.c
> +++ b/drivers/ntb/ntb_transport.c
> @@ -1128,8 +1128,8 @@ static int ntb_transport_probe(struct ntb_client *self, struct
> ntb_dev *ndev)
>  	qp_count = ilog2(qp_bitmap);
>  	if (max_num_clients && max_num_clients < qp_count)
>  		qp_count = max_num_clients;
> -	else if (mw_count < qp_count)
> -		qp_count = mw_count;
> +	else if (nt->mw_count < qp_count)
> +		qp_count = nt->mw_count;
> 
>  	qp_bitmap &= BIT_ULL(qp_count) - 1;
> 
> --
> 2.11.0