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[for-rc,1/5] IB/rdmavt: Fix alloc_qpn() WARN_ON()

Message ID 20190524154438.10588.41702.stgit@awfm-01.aw.intel.com (mailing list archive)
State Accepted
Delegated to: Jason Gunthorpe
Headers show
Series Patches for 5.2 rc cycle | expand

Commit Message

Dennis Dalessandro May 24, 2019, 3:44 p.m. UTC 
From: Mike Marciniszyn <mike.marciniszyn@intel.com>

The qpn allocation logic has a WARN_ON() that intends to detect the
use of an index that will introduce bits in the lower order bits
of the QOS bits in the QPN.

Unfortunately, it has the following bugs:
- it misfires when wrapping QPN allocation for non-QOS
- it doesn't correctly detect low order QOS bits (despite the comment)

The WARN_ON() should not be applied to non-QOS (qos_shift == 1).

Additionally, it SHOULD test the qpn bits per the table below:

2 data VLs:   [qp7, qp6, qp5, qp4, qp3, qp2, qp1] ^
              [  0,   0,   0,   0,   0,   0, sc0],  qp bit 1 always 0*
3-4 data VLs: [qp7, qp6, qp5, qp4, qp3, qp2, qp1] ^
              [  0,   0,   0,   0,   0, sc1, sc0], qp bits [21] always 0
5-8 data VLs: [qp7, qp6, qp5, qp4, qp3, qp2, qp1] ^
              [  0,   0,   0,   0, sc2, sc1, sc0] qp bits [321] always 0

Fix by qualifying the warning for qos_shift > 1 and producing the correct
mask to insure the above bits are zero without generating a superfluous
warning.

Fixes: 501edc42446e ("IB/rdmavt: Correct warning during QPN allocation")
Reviewed-by: Kaike Wan <kaike.wan@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
---
 drivers/infiniband/sw/rdmavt/qp.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
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Patch

diff --git a/drivers/infiniband/sw/rdmavt/qp.c b/drivers/infiniband/sw/rdmavt/qp.c
index 31a2e65..c5a5061 100644
--- a/drivers/infiniband/sw/rdmavt/qp.c
+++ b/drivers/infiniband/sw/rdmavt/qp.c
@@ -594,7 +594,8 @@  static int alloc_qpn(struct rvt_dev_info *rdi, struct rvt_qpn_table *qpt,
 			offset = qpt->incr | ((offset & 1) ^ 1);
 		}
 		/* there can be no set bits in low-order QoS bits */
-		WARN_ON(offset & (BIT(rdi->dparms.qos_shift) - 1));
+		WARN_ON(rdi->dparms.qos_shift > 1 &&
+			offset & ((BIT(rdi->dparms.qos_shift - 1) - 1) << 1));
 		qpn = mk_qpn(qpt, map, offset);
 	}