IB/mlx5: Fix micro UAR allocator

The micro UAR (uuar) allocator had a bug which resulted from the fact
that in each UAR we only have two micro UARs avaialable, those at
index 0 and 1.  This patch defines iterators to aid in traversing the
list of available micro UARs when allocating a uuar.

In addition, change the logic in create_user_qp() so that if high
class allocation fails (high class means lower latency), we revert to
medium class and not to the low class.
Signed-off-by: Eli Cohen <eli@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/hw/mlx5/main.c

@@ -541,6 +541,7 @@ static struct ib_ucontext *mlx5_ib_alloc_ucontext(struct ib_device *ibdev,
 	struct mlx5_ib_ucontext *context;
 	struct mlx5_uuar_info *uuari;
 	struct mlx5_uar *uars;
+	int gross_uuars;
 	int num_uars;
 	int uuarn;
 	int err;
@@ -559,11 +560,13 @@ static struct ib_ucontext *mlx5_ib_alloc_ucontext(struct ib_device *ibdev,
 	if (req.total_num_uuars == 0)
 		return ERR_PTR(-EINVAL);
 
-	req.total_num_uuars = ALIGN(req.total_num_uuars, MLX5_BF_REGS_PER_PAGE);
+	req.total_num_uuars = ALIGN(req.total_num_uuars,
+				    MLX5_NON_FP_BF_REGS_PER_PAGE);
 	if (req.num_low_latency_uuars > req.total_num_uuars - 1)
 		return ERR_PTR(-EINVAL);
 
-	num_uars = req.total_num_uuars / MLX5_BF_REGS_PER_PAGE;
+	num_uars = req.total_num_uuars / MLX5_NON_FP_BF_REGS_PER_PAGE;
+	gross_uuars = num_uars * MLX5_BF_REGS_PER_PAGE;
 	resp.qp_tab_size      = 1 << dev->mdev.caps.log_max_qp;
 	resp.bf_reg_size      = dev->mdev.caps.bf_reg_size;
 	resp.cache_line_size  = L1_CACHE_BYTES;
@@ -585,7 +588,7 @@ static struct ib_ucontext *mlx5_ib_alloc_ucontext(struct ib_device *ibdev,
 		goto out_ctx;
 	}
 
-	uuari->bitmap = kcalloc(BITS_TO_LONGS(req.total_num_uuars),
+	uuari->bitmap = kcalloc(BITS_TO_LONGS(gross_uuars),
 				sizeof(*uuari->bitmap),
 				GFP_KERNEL);
 	if (!uuari->bitmap) {
@@ -595,13 +598,13 @@ static struct ib_ucontext *mlx5_ib_alloc_ucontext(struct ib_device *ibdev,
 	/*
 	 * clear all fast path uuars
 	 */
-	for (i = 0; i < req.total_num_uuars; i++) {
+	for (i = 0; i < gross_uuars; i++) {
 		uuarn = i & 3;
 		if (uuarn == 2 || uuarn == 3)
 			set_bit(i, uuari->bitmap);
 	}
 
-	uuari->count = kcalloc(req.total_num_uuars, sizeof(*uuari->count), GFP_KERNEL);
+	uuari->count = kcalloc(gross_uuars, sizeof(*uuari->count), GFP_KERNEL);
 	if (!uuari->count) {
 		err = -ENOMEM;
 		goto out_bitmap;

drivers/infiniband/hw/mlx5/qp.c

@@ -340,14 +340,57 @@ static int qp_has_rq(struct ib_qp_init_attr *attr)
 	return 1;
 }
 
+static int first_med_uuar(void)
+{
+	return 1;
+}
+
+static int next_uuar(int n)
+{
+	n++;
+
+	while (((n % 4) & 2))
+		n++;
+
+	return n;
+}
+
+static int num_med_uuar(struct mlx5_uuar_info *uuari)
+{
+	int n;
+
+	n = uuari->num_uars * MLX5_NON_FP_BF_REGS_PER_PAGE -
+		uuari->num_low_latency_uuars - 1;
+
+	return n >= 0 ? n : 0;
+}
+
+static int max_uuari(struct mlx5_uuar_info *uuari)
+{
+	return uuari->num_uars * 4;
+}
+
+static int first_hi_uuar(struct mlx5_uuar_info *uuari)
+{
+	int med;
+	int i;
+	int t;
+
+	med = num_med_uuar(uuari);
+	for (t = 0, i = first_med_uuar();; i = next_uuar(i)) {
+		t++;
+		if (t == med)
+			return next_uuar(i);
+	}
+
+	return 0;
+}
+
 static int alloc_high_class_uuar(struct mlx5_uuar_info *uuari)
 {
-	int nuuars = uuari->num_uars * MLX5_BF_REGS_PER_PAGE;
-	int start_uuar;
 	int i;
 
-	start_uuar = nuuars - uuari->num_low_latency_uuars;
-	for (i = start_uuar; i < nuuars; i++) {
+	for (i = first_hi_uuar(uuari); i < max_uuari(uuari); i = next_uuar(i)) {
 		if (!test_bit(i, uuari->bitmap)) {
 			set_bit(i, uuari->bitmap);
 			uuari->count[i]++;
@@ -360,19 +403,10 @@ static int alloc_high_class_uuar(struct mlx5_uuar_info *uuari)
 
 static int alloc_med_class_uuar(struct mlx5_uuar_info *uuari)
 {
-	int nuuars = uuari->num_uars * MLX5_BF_REGS_PER_PAGE;
-	int minidx = 1;
-	int uuarn;
-	int end;
+	int minidx = first_med_uuar();
 	int i;
 
-	end = nuuars - uuari->num_low_latency_uuars;
-
-	for (i = 1; i < end; i++) {
-		uuarn = i & 3;
-		if (uuarn == 2 || uuarn == 3)
-			continue;
-
+	for (i = first_med_uuar(); i < first_hi_uuar(uuari); i = next_uuar(i)) {
 		if (uuari->count[i] < uuari->count[minidx])
 			minidx = i;
 	}
@@ -510,13 +544,18 @@ static int create_user_qp(struct mlx5_ib_dev *dev, struct ib_pd *pd,
 	uuarn = alloc_uuar(&context->uuari, MLX5_IB_LATENCY_CLASS_HIGH);
 	if (uuarn < 0) {
 		mlx5_ib_dbg(dev, "failed to allocate low latency UUAR\n");
+		mlx5_ib_dbg(dev, "reverting to medium latency\n");
+		uuarn = alloc_uuar(&context->uuari, MLX5_IB_LATENCY_CLASS_MEDIUM);
+		if (uuarn < 0) {
+			mlx5_ib_dbg(dev, "failed to allocate medium latency UUAR\n");
 			mlx5_ib_dbg(dev, "reverting to high latency\n");
 			uuarn = alloc_uuar(&context->uuari, MLX5_IB_LATENCY_CLASS_LOW);
 			if (uuarn < 0) {
-			mlx5_ib_dbg(dev, "uuar allocation failed\n");
+				mlx5_ib_warn(dev, "uuar allocation failed\n");
 				return uuarn;
 			}
 		}
+	}
 
 	uar_index = uuarn_to_uar_index(&context->uuari, uuarn);
 	mlx5_ib_dbg(dev, "uuarn 0x%x, uar_index 0x%x\n", uuarn, uar_index);

include/linux/mlx5/device.h

@@ -106,7 +106,8 @@ enum {
 enum {
 	MLX5_BF_REGS_PER_PAGE		= 4,
 	MLX5_MAX_UAR_PAGES		= 1 << 8,
-	MLX5_MAX_UUARS		= MLX5_MAX_UAR_PAGES * MLX5_BF_REGS_PER_PAGE,
+	MLX5_NON_FP_BF_REGS_PER_PAGE	= 2,
+	MLX5_MAX_UUARS	= MLX5_MAX_UAR_PAGES * MLX5_NON_FP_BF_REGS_PER_PAGE,
 };
 
 enum {