RE: [PATCH 1/2] ntb_transport: Fix bug with max_mw_size parameter

[Allen Hubbe]

From: Logan Gunthorpe
> When using the max_mw_size parameter of ntb_transport to limit the size of
> the Memory windows, communication cannot be established and the queues
> freeze.
> 
> This is because the mw_size that's reported to the peer is correctly
> limited but the size used locally is not. So the MW is initialized
> with a buffer smaller than the window but the TX side is using the
> full window. This means the TX side will be writing to a region of the
> window that points nowhere.
> 
> This is easily fixed by applying the same limit to tx_size in
> ntb_transport_init_queue().
> 
> Fixes: e26a5843f7f5 ("NTB: Split ntb_hw_intel and ntb_transport drivers")
> Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
> Cc: Jon Mason <jdmason@xxxxxxxx>
> Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
> Cc: Allen Hubbe <Allen.Hubbe@xxxxxxx>

Acked-by: Allen Hubbe <Allen.Hubbe@xxxxxxxx>

> ---
>  drivers/ntb/ntb_transport.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/ntb/ntb_transport.c b/drivers/ntb/ntb_transport.c
> index 045e3dd4750e..9878c48826e3 100644
> --- a/drivers/ntb/ntb_transport.c
> +++ b/drivers/ntb/ntb_transport.c
> @@ -1003,6 +1003,9 @@ static int ntb_transport_init_queue(struct ntb_transport_ctx *nt,
>  	mw_base = nt->mw_vec[mw_num].phys_addr;
>  	mw_size = nt->mw_vec[mw_num].phys_size;
> 
> +	if (max_mw_size && mw_size > max_mw_size)
> +		mw_size = max_mw_size;
> +
>  	tx_size = (unsigned int)mw_size / num_qps_mw;
>  	qp_offset = tx_size * (qp_num / mw_count);
> 
> --
> 2.11.0