[PATCH 3.16 274/366] RDMA/mlx5: Don't assume that medium blueFlame register exists

[Ben Hutchings]

3.16.60-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Yishai Hadas <yishaih@xxxxxxxxxxxx>

commit 18b0362e87dfa09e355093b897b9db854e360d28 upstream.

User can leave system without medium BlueFlames registers,
however the code assumed that at least one such register exists.

This patch fixes that assumption.

Fixes: c1be5232d21d ("IB/mlx5: Fix micro UAR allocator")
Reported-by: Rohit Zambre <rzambre@xxxxxxx>
Signed-off-by: Yishai Hadas <yishaih@xxxxxxxxxxxx>
Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxxxx>
Signed-off-by: Doug Ledford <dledford@xxxxxxxxxx>
[bwh: Backported to 3.16:
 - s/bfreg/uuar/g
 - Neither alloc_med_class_uuar() nor num_med_uuar() takes a mlx5_ib_dev
   pointer, so first_med_uuar() doesn't need to take one
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/infiniband/hw/mlx5/qp.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

--- a/drivers/infiniband/hw/mlx5/qp.c
+++ b/drivers/infiniband/hw/mlx5/qp.c
@@ -356,11 +356,6 @@ static int qp_has_rq(struct ib_qp_init_a
 	return 1;
 }
 
-static int first_med_uuar(void)
-{
-	return 1;
-}
-
 static int next_uuar(int n)
 {
 	n++;
@@ -395,6 +390,11 @@ static int max_uuari(struct mlx5_uuar_in
 	return uuari->num_uars * 4;
 }
 
+static int first_med_uuar(struct mlx5_uuar_info *uuari)
+{
+	return num_med_uuar(uuari) ? 1 : -ENOMEM;
+}
+
 static int first_hi_uuar(struct mlx5_uuar_info *uuari)
 {
 	int med;
@@ -420,10 +420,13 @@ static int alloc_high_class_uuar(struct
 
 static int alloc_med_class_uuar(struct mlx5_uuar_info *uuari)
 {
-	int minidx = first_med_uuar();
+	int minidx = first_med_uuar(uuari);
 	int i;
 
-	for (i = first_med_uuar(); i < first_hi_uuar(uuari); i = next_uuar(i)) {
+	if (minidx < 0)
+		return minidx;
+
+	for (i = minidx; i < first_hi_uuar(uuari); i = next_uuar(i)) {
 		if (uuari->count[i] < uuari->count[minidx])
 			minidx = i;
 		if (!uuari->count[minidx])