[PATCH 4.9 75/84] ntb_transport: fix qp count bug

Greg Kroah-Hartman
2017-08-28T08:13:10Z

From: Logan Gunthorpe <logang@deltatee.com>

commit cb827ee6ccc3e480f0d9c0e8e53eef55be5b0414 upstream.

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>
Fixes: e26a5843f7f5 ("NTB: Split ntb_hw_intel and ntb_transport drivers")
Acked-by: Allen Hubbe <Allen.Hubbe@dell.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/ntb/ntb_transport.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/ntb/ntb_transport.c
+++ b/drivers/ntb/ntb_transport.c
@@ -1125,8 +1125,8 @@ static int ntb_transport_probe(struct nt
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;