Date:   Mon, 16 May 2022 11:47:35 +0300
From:   Eli Cohen <elic@...dia.com>
To:     <mst@...hat.com>, <jasowang@...hat.com>
CC:     <virtualization@...ts.linux-foundation.org>,
        <linux-kernel@...r.kernel.org>, <si-wei.liu@...cle.com>,
        Eli Cohen <elic@...dia.com>
Subject: [PATCH] vdpa/mlx5: Use consistent RQT size

The current code evaluates RQT size based on the configured number of
virtqueues. This can raise an issue in the following scenario:

Assume MQ was negotiated.
1. mlx5_vdpa_set_map() gets called.
2. handle_ctrl_mq() is called setting cur_num_vqs to some value, lower
   than the configured max VQs.
3. A second set_map gets called, but now a smaller number of VQs is used
   to evaluate the size of the RQT.
4. handle_ctrl_mq() is called with a value larger than what the RQT can
   hold. This will emit errors and the driver state is compromised.

To fix this, we use a new field in struct mlx5_vdpa_net to hold the
required number of entries in the RQT. This value is evaluated in
mlx5_vdpa_set_driver_features() where we have the negotiated features
all set up.

In addition to that, we take into consideration the max capability of RQT
entries early when the device is added so we don't need to take consider
it when creating the RQT.

Last, we remove the use of mlx5_vdpa_max_qps() which just returns the
max_vas / 2 and make the code clearer.

Fixes: 52893733f2c5 ("vdpa/mlx5: Add multiqueue support")
Acked-by: Jason Wang <jasowang@...hat.com>
Signed-off-by: Eli Cohen <elic@...dia.com>
---
 drivers/vdpa/mlx5/net/mlx5_vnet.c | 61 +++++++++++--------------------
 1 file changed, 21 insertions(+), 40 deletions(-)

diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
index 79001301b383..e0de44000d92 100644
--- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
+++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
@@ -161,6 +161,7 @@ struct mlx5_vdpa_net {
 	struct mlx5_flow_handle *rx_rule_mcast;
 	bool setup;
 	u32 cur_num_vqs;
+	u32 rqt_size;
 	struct notifier_block nb;
 	struct vdpa_callback config_cb;
 	struct mlx5_vdpa_wq_ent cvq_ent;
@@ -204,17 +205,12 @@ static __virtio16 cpu_to_mlx5vdpa16(struct mlx5_vdpa_dev *mvdev, u16 val)
 	return __cpu_to_virtio16(mlx5_vdpa_is_little_endian(mvdev), val);
 }
 
-static inline u32 mlx5_vdpa_max_qps(int max_vqs)
-{
-	return max_vqs / 2;
-}
-
 static u16 ctrl_vq_idx(struct mlx5_vdpa_dev *mvdev)
 {
 	if (!(mvdev->actual_features & BIT_ULL(VIRTIO_NET_F_MQ)))
 		return 2;
 
-	return 2 * mlx5_vdpa_max_qps(mvdev->max_vqs);
+	return mvdev->max_vqs;
 }
 
 static bool is_ctrl_vq_idx(struct mlx5_vdpa_dev *mvdev, u16 idx)
@@ -1236,25 +1232,13 @@ static void teardown_vq(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *
 static int create_rqt(struct mlx5_vdpa_net *ndev)
 {
 	__be32 *list;
-	int max_rqt;
 	void *rqtc;
 	int inlen;
 	void *in;
 	int i, j;
 	int err;
-	int num;
-
-	if (!(ndev->mvdev.actual_features & BIT_ULL(VIRTIO_NET_F_MQ)))
-		num = 1;
-	else
-		num = ndev->cur_num_vqs / 2;
 
-	max_rqt = min_t(int, roundup_pow_of_two(num),
-			1 << MLX5_CAP_GEN(ndev->mvdev.mdev, log_max_rqt_size));
-	if (max_rqt < 1)
-		return -EOPNOTSUPP;
-
-	inlen = MLX5_ST_SZ_BYTES(create_rqt_in) + max_rqt * MLX5_ST_SZ_BYTES(rq_num);
+	inlen = MLX5_ST_SZ_BYTES(create_rqt_in) + ndev->rqt_size * MLX5_ST_SZ_BYTES(rq_num);
 	in = kzalloc(inlen, GFP_KERNEL);
 	if (!in)
 		return -ENOMEM;
@@ -1263,12 +1247,12 @@ static int create_rqt(struct mlx5_vdpa_net *ndev)
 	rqtc = MLX5_ADDR_OF(create_rqt_in, in, rqt_context);
 
 	MLX5_SET(rqtc, rqtc, list_q_type, MLX5_RQTC_LIST_Q_TYPE_VIRTIO_NET_Q);
-	MLX5_SET(rqtc, rqtc, rqt_max_size, max_rqt);
+	MLX5_SET(rqtc, rqtc, rqt_max_size, ndev->rqt_size);
 	list = MLX5_ADDR_OF(rqtc, rqtc, rq_num[0]);
-	for (i = 0, j = 0; i < max_rqt; i++, j += 2)
-		list[i] = cpu_to_be32(ndev->vqs[j % (2 * num)].virtq_id);
+	for (i = 0, j = 0; i < ndev->rqt_size; i++, j += 2)
+		list[i] = cpu_to_be32(ndev->vqs[j % ndev->cur_num_vqs].virtq_id);
 
-	MLX5_SET(rqtc, rqtc, rqt_actual_size, max_rqt);
+	MLX5_SET(rqtc, rqtc, rqt_actual_size, ndev->rqt_size);
 	err = mlx5_vdpa_create_rqt(&ndev->mvdev, in, inlen, &ndev->res.rqtn);
 	kfree(in);
 	if (err)
@@ -1282,19 +1266,13 @@ static int create_rqt(struct mlx5_vdpa_net *ndev)
 static int modify_rqt(struct mlx5_vdpa_net *ndev, int num)
 {
 	__be32 *list;
-	int max_rqt;
 	void *rqtc;
 	int inlen;
 	void *in;
 	int i, j;
 	int err;
 
-	max_rqt = min_t(int, roundup_pow_of_two(ndev->cur_num_vqs / 2),
-			1 << MLX5_CAP_GEN(ndev->mvdev.mdev, log_max_rqt_size));
-	if (max_rqt < 1)
-		return -EOPNOTSUPP;
-
-	inlen = MLX5_ST_SZ_BYTES(modify_rqt_in) + max_rqt * MLX5_ST_SZ_BYTES(rq_num);
+	inlen = MLX5_ST_SZ_BYTES(modify_rqt_in) + ndev->rqt_size * MLX5_ST_SZ_BYTES(rq_num);
 	in = kzalloc(inlen, GFP_KERNEL);
 	if (!in)
 		return -ENOMEM;
@@ -1305,10 +1283,10 @@ static int modify_rqt(struct mlx5_vdpa_net *ndev, int num)
 	MLX5_SET(rqtc, rqtc, list_q_type, MLX5_RQTC_LIST_Q_TYPE_VIRTIO_NET_Q);
 
 	list = MLX5_ADDR_OF(rqtc, rqtc, rq_num[0]);
-	for (i = 0, j = 0; i < max_rqt; i++, j += 2)
+	for (i = 0, j = 0; i < ndev->rqt_size; i++, j += 2)
 		list[i] = cpu_to_be32(ndev->vqs[j % num].virtq_id);
 
-	MLX5_SET(rqtc, rqtc, rqt_actual_size, max_rqt);
+	MLX5_SET(rqtc, rqtc, rqt_actual_size, ndev->rqt_size);
 	err = mlx5_vdpa_modify_rqt(&ndev->mvdev, in, inlen, ndev->res.rqtn);
 	kfree(in);
 	if (err)
@@ -1625,7 +1603,7 @@ static virtio_net_ctrl_ack handle_ctrl_mq(struct mlx5_vdpa_dev *mvdev, u8 cmd)
 
 		newqps = mlx5vdpa16_to_cpu(mvdev, mq.virtqueue_pairs);
 		if (newqps < VIRTIO_NET_CTRL_MQ_VQ_PAIRS_MIN ||
-		    newqps > mlx5_vdpa_max_qps(mvdev->max_vqs))
+		    newqps > ndev->rqt_size)
 			break;
 
 		if (ndev->cur_num_vqs == 2 * newqps) {
@@ -1989,7 +1967,7 @@ static int setup_virtqueues(struct mlx5_vdpa_dev *mvdev)
 	int err;
 	int i;
 
-	for (i = 0; i < 2 * mlx5_vdpa_max_qps(mvdev->max_vqs); i++) {
+	for (i = 0; i < mvdev->max_vqs; i++) {
 		err = setup_vq(ndev, &ndev->vqs[i]);
 		if (err)
 			goto err_vq;
@@ -2060,9 +2038,11 @@ static int mlx5_vdpa_set_driver_features(struct vdpa_device *vdev, u64 features)
 
 	ndev->mvdev.actual_features = features & ndev->mvdev.mlx_features;
 	if (ndev->mvdev.actual_features & BIT_ULL(VIRTIO_NET_F_MQ))
-		ndev->cur_num_vqs = 2 * mlx5vdpa16_to_cpu(mvdev, ndev->config.max_virtqueue_pairs);
+		ndev->rqt_size = mlx5vdpa16_to_cpu(mvdev, ndev->config.max_virtqueue_pairs);
 	else
-		ndev->cur_num_vqs = 2;
+		ndev->rqt_size = 1;
+
+	ndev->cur_num_vqs = 2 * ndev->rqt_size;
 
 	update_cvq_info(mvdev);
 	return err;
@@ -2529,7 +2509,7 @@ static void init_mvqs(struct mlx5_vdpa_net *ndev)
 	struct mlx5_vdpa_virtqueue *mvq;
 	int i;
 
-	for (i = 0; i < 2 * mlx5_vdpa_max_qps(ndev->mvdev.max_vqs); ++i) {
+	for (i = 0; i < ndev->mvdev.max_vqs; ++i) {
 		mvq = &ndev->vqs[i];
 		memset(mvq, 0, offsetof(struct mlx5_vdpa_virtqueue, ri));
 		mvq->index = i;
@@ -2671,7 +2651,8 @@ static int mlx5_vdpa_dev_add(struct vdpa_mgmt_dev *v_mdev, const char *name,
 		return -EOPNOTSUPP;
 	}
 
-	max_vqs = MLX5_CAP_DEV_VDPA_EMULATION(mdev, max_num_virtio_queues);
+	max_vqs = min_t(int, MLX5_CAP_DEV_VDPA_EMULATION(mdev, max_num_virtio_queues),
+			1 << MLX5_CAP_GEN(mdev, log_max_rqt_size));
 	if (max_vqs < 2) {
 		dev_warn(mdev->device,
 			 "%d virtqueues are supported. At least 2 are required\n",
@@ -2742,7 +2723,7 @@ static int mlx5_vdpa_dev_add(struct vdpa_mgmt_dev *v_mdev, const char *name,
 		ndev->mvdev.mlx_features |= BIT_ULL(VIRTIO_NET_F_MAC);
 	}
 
-	config->max_virtqueue_pairs = cpu_to_mlx5vdpa16(mvdev, mlx5_vdpa_max_qps(max_vqs));
+	config->max_virtqueue_pairs = cpu_to_mlx5vdpa16(mvdev, max_vqs / 2);
 	mvdev->vdev.dma_dev = &mdev->pdev->dev;
 	err = mlx5_vdpa_alloc_resources(&ndev->mvdev);
 	if (err)
@@ -2769,7 +2750,7 @@ static int mlx5_vdpa_dev_add(struct vdpa_mgmt_dev *v_mdev, const char *name,
 	ndev->nb.notifier_call = event_handler;
 	mlx5_notifier_register(mdev, &ndev->nb);
 	mvdev->vdev.mdev = &mgtdev->mgtdev;
-	err = _vdpa_register_device(&mvdev->vdev, 2 * mlx5_vdpa_max_qps(max_vqs) + 1);
+	err = _vdpa_register_device(&mvdev->vdev, max_vqs + 1);
 	if (err)
 		goto err_reg;
 
-- 
2.35.1

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