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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "stable@vger.kernel.org" <stable@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC:     Logan Gunthorpe <logang@deltatee.com>,
        Dave Jiang <dave.jiang@intel.com>,
        Jon Mason <jdmason@kudzu.us>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL for 4.9 250/293] ntb_transport: Fix bug with
 max_mw_size parameter
Thread-Topic: [PATCH AUTOSEL for 4.9 250/293] ntb_transport: Fix bug with
 max_mw_size parameter
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Date:   Mon, 9 Apr 2018 00:26:07 +0000
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From: Logan Gunthorpe <logang@deltatee.com>

[ Upstream commit cbd27448faff4843ac4b66cc71445a10623ff48d ]

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@deltatee.com>
Acked-by: Allen Hubbe <Allen.Hubbe@dell.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 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 24222a5d8df2..da95bd8f0f72 100644
--- a/drivers/ntb/ntb_transport.c
+++ b/drivers/ntb/ntb_transport.c
@@ -996,6 +996,9 @@ static int ntb_transport_init_queue(struct ntb_transpor=
t_ctx *nt,
 	mw_base =3D nt->mw_vec[mw_num].phys_addr;
 	mw_size =3D nt->mw_vec[mw_num].phys_size;
=20
+	if (max_mw_size && mw_size > max_mw_size)
+		mw_size =3D max_mw_size;
+
 	tx_size =3D (unsigned int)mw_size / num_qps_mw;
 	qp_offset =3D tx_size * (qp_num / mw_count);
=20
--=20
2.15.1