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Subject[PATCH AUTOSEL for 4.15 105/189] ntb_transport: Fix bug with max_mw_size parameter
From: Logan Gunthorpe <>

[ 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

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

Fixes: e26a5843f7f5 ("NTB: Split ntb_hw_intel and ntb_transport drivers")
Signed-off-by: Logan Gunthorpe <>
Acked-by: Allen Hubbe <>
Cc: Dave Jiang <>
Signed-off-by: Jon Mason <>
Signed-off-by: Sasha Levin <>
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);

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