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From:   Eli Cohen <elic@nvidia.com>
To:     <eperezma@redhat.com>, <jasowang@redhat.com>, <mst@redhat.com>,
        <virtualization@lists.linux-foundation.org>
CC:     <linux-kernel@vger.kernel.org>, <si-wei.liu@oracle.com>,
        <parav@nvidia.com>, Eli Cohen <elic@nvidia.com>
Subject: [PATCH RFC v1 1/3] vdpa/mlx5: Implement susupend virtqueue callback
Date:   Mon, 20 Jun 2022 16:06:12 +0300
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Implement the suspend callback allowing to suspend the virtqueues so
they stop processing descriptors. This is required to allow to query a
consistent state of the virtqueue while live migration is taking place.

Signed-off-by: Eli Cohen <elic@nvidia.com>
---
 drivers/vdpa/mlx5/net/mlx5_vnet.c  | 68 +++++++++++++++++++++++++++++-
 include/linux/mlx5/mlx5_ifc_vdpa.h |  8 ++++
 2 files changed, 75 insertions(+), 1 deletion(-)

diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
index fb0b23e71383..ea4bc8a0cd25 100644
--- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
+++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
@@ -895,6 +895,7 @@ static int create_virtqueue(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtque
 	if (err)
 		goto err_cmd;
 
+	mvq->fw_state = MLX5_VIRTIO_NET_Q_OBJECT_STATE_INIT;
 	kfree(in);
 	mvq->virtq_id = MLX5_GET(general_obj_out_cmd_hdr, out, obj_id);
 
@@ -922,6 +923,7 @@ static void destroy_virtqueue(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtq
 		mlx5_vdpa_warn(&ndev->mvdev, "destroy virtqueue 0x%x\n", mvq->virtq_id);
 		return;
 	}
+	mvq->fw_state = MLX5_VIRTIO_NET_Q_OBJECT_NONE;
 	umems_destroy(ndev, mvq);
 }
 
@@ -1121,6 +1123,20 @@ static int query_virtqueue(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueu
 	return err;
 }
 
+static bool is_valid_state_change(int oldstate, int newstate)
+{
+	switch (oldstate) {
+	case MLX5_VIRTIO_NET_Q_OBJECT_STATE_INIT:
+		return newstate == MLX5_VIRTIO_NET_Q_OBJECT_STATE_RDY;
+	case MLX5_VIRTIO_NET_Q_OBJECT_STATE_RDY:
+		return newstate == MLX5_VIRTIO_NET_Q_OBJECT_STATE_SUSPEND;
+	case MLX5_VIRTIO_NET_Q_OBJECT_STATE_SUSPEND:
+	case MLX5_VIRTIO_NET_Q_OBJECT_STATE_ERR:
+	default:
+		return false;
+	}
+}
+
 static int modify_virtqueue(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *mvq, int state)
 {
 	int inlen = MLX5_ST_SZ_BYTES(modify_virtio_net_q_in);
@@ -1130,6 +1146,12 @@ static int modify_virtqueue(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtque
 	void *in;
 	int err;
 
+	if (mvq->fw_state == MLX5_VIRTIO_NET_Q_OBJECT_NONE)
+		return 0;
+
+	if (!is_valid_state_change(mvq->fw_state, state))
+		return -EINVAL;
+
 	in = kzalloc(inlen, GFP_KERNEL);
 	if (!in)
 		return -ENOMEM;
@@ -1991,6 +2013,7 @@ static void mlx5_vdpa_set_vq_ready(struct vdpa_device *vdev, u16 idx, bool ready
 	struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
 	struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
 	struct mlx5_vdpa_virtqueue *mvq;
+	int err;
 
 	if (!mvdev->actual_features)
 		return;
@@ -2004,8 +2027,16 @@ static void mlx5_vdpa_set_vq_ready(struct vdpa_device *vdev, u16 idx, bool ready
 	}
 
 	mvq = &ndev->vqs[idx];
-	if (!ready)
+	if (!ready) {
 		suspend_vq(ndev, mvq);
+	} else {
+		err = modify_virtqueue(ndev, mvq, MLX5_VIRTIO_NET_Q_OBJECT_STATE_RDY);
+		if (err) {
+			mlx5_vdpa_warn(mvdev, "modify VQ %d to ready failed (%d)\n", idx, err);
+			ready = false;
+		}
+	}
+
 
 	mvq->ready = ready;
 }
@@ -2732,6 +2763,39 @@ static int mlx5_vdpa_get_vendor_vq_stats(struct vdpa_device *vdev, u16 idx,
 	return err;
 }
 
+static void mlx5_vdpa_cvq_suspend(struct mlx5_vdpa_dev *mvdev, bool suspend)
+{
+	struct mlx5_control_vq *cvq;
+
+	if (!(mvdev->actual_features & BIT_ULL(VIRTIO_NET_F_CTRL_VQ)))
+		return;
+
+	cvq = &mvdev->cvq;
+	cvq->ready = !suspend;
+}
+
+static int mlx5_vdpa_suspend(struct vdpa_device *vdev, bool suspend)
+{
+	struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
+	struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
+	struct mlx5_vdpa_virtqueue *mvq;
+	int i;
+
+	if (!suspend) {
+		mlx5_vdpa_warn(mvdev, "Resume of virtqueues is not supported\n");
+		return -EOPNOTSUPP;
+	}
+
+	down_write(&ndev->reslock);
+	for (i = 0; i < ndev->cur_num_vqs; i++) {
+		mvq = &ndev->vqs[i];
+		suspend_vq(ndev, mvq);
+	}
+	mlx5_vdpa_cvq_suspend(mvdev, suspend);
+	up_write(&ndev->reslock);
+	return 0;
+}
+
 static const struct vdpa_config_ops mlx5_vdpa_ops = {
 	.set_vq_address = mlx5_vdpa_set_vq_address,
 	.set_vq_num = mlx5_vdpa_set_vq_num,
@@ -2762,6 +2826,7 @@ static const struct vdpa_config_ops mlx5_vdpa_ops = {
 	.get_generation = mlx5_vdpa_get_generation,
 	.set_map = mlx5_vdpa_set_map,
 	.free = mlx5_vdpa_free,
+	.suspend = mlx5_vdpa_suspend,
 };
 
 static int query_mtu(struct mlx5_core_dev *mdev, u16 *mtu)
@@ -2827,6 +2892,7 @@ static void init_mvqs(struct mlx5_vdpa_net *ndev)
 		mvq->index = i;
 		mvq->ndev = ndev;
 		mvq->fwqp.fw = true;
+		mvq->fw_state = MLX5_VIRTIO_NET_Q_OBJECT_NONE;
 	}
 	for (; i < ndev->mvdev.max_vqs; i++) {
 		mvq = &ndev->vqs[i];
diff --git a/include/linux/mlx5/mlx5_ifc_vdpa.h b/include/linux/mlx5/mlx5_ifc_vdpa.h
index 4414ed5b6ed2..9becdc3fa503 100644
--- a/include/linux/mlx5/mlx5_ifc_vdpa.h
+++ b/include/linux/mlx5/mlx5_ifc_vdpa.h
@@ -150,6 +150,14 @@ enum {
 	MLX5_VIRTIO_NET_Q_OBJECT_STATE_ERR      = 0x3,
 };
 
+/* This indicates that the object was not created or has already
+ * been desroyed. It is very safe to assume that this object will never
+ * have so many states
+ */
+enum {
+	MLX5_VIRTIO_NET_Q_OBJECT_NONE = 0xffffffff
+};
+
 enum {
 	MLX5_RQTC_LIST_Q_TYPE_RQ            = 0x0,
 	MLX5_RQTC_LIST_Q_TYPE_VIRTIO_NET_Q  = 0x1,
-- 
2.35.1