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Message-ID: <DM8PR12MB54001E9C39450E33CE7CAFACAB1F9@DM8PR12MB5400.namprd12.prod.outlook.com>
Date: Wed, 30 Mar 2022 06:52:12 +0000
From: Eli Cohen <elic@...dia.com>
To: Jason Wang <jasowang@...hat.com>, "mst@...hat.com" <mst@...hat.com>
CC: "hdanton@...a.com" <hdanton@...a.com>,
"virtualization@...ts.linux-foundation.org"
<virtualization@...ts.linux-foundation.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH RESEND V2 2/3] vdpa: mlx5: synchronize driver status with
CVQ
> From: Jason Wang <jasowang@...hat.com>
> Sent: Tuesday, March 29, 2022 7:21 AM
> To: jasowang@...hat.com; mst@...hat.com
> Cc: Eli Cohen <elic@...dia.com>; hdanton@...a.com; virtualization@...ts.linux-foundation.org; linux-kernel@...r.kernel.org
> Subject: [PATCH RESEND V2 2/3] vdpa: mlx5: synchronize driver status with CVQ
>
> Currently, CVQ doesn't have any synchronization with the driver
> status. Then CVQ emulation code run in the middle of:
>
> 1) device reset
> 2) device status changed
> 3) map updating
>
> The will lead several unexpected issue like trying to execute CVQ
> command after the driver has been teared down.
>
> Fixing this by using reslock to synchronize CVQ emulation code with
> the driver status changing:
>
> - protect the whole device reset, status changing and set_map()
> updating with reslock
> - protect the CVQ handler with the reslock and check
> VIRTIO_CONFIG_S_DRIVER_OK in the CVQ handler
>
> This will guarantee that:
>
> 1) CVQ handler won't work if VIRTIO_CONFIG_S_DRIVER_OK is not set
> 2) CVQ handler will see a consistent state of the driver instead of
> the partial one when it is running in the middle of the
> teardown_driver() or setup_driver().
>
> Cc: 5262912ef3cfc ("vdpa/mlx5: Add support for control VQ and MAC setting")
> Signed-off-by: Jason Wang <jasowang@...hat.com>
Acked-by: Eli Cohen <elic@...dia.com>
> ---
> Changes since V1:
> - document the lock requirement
> - protect the whole .set_map()
> ---
> drivers/vdpa/mlx5/net/mlx5_vnet.c | 51 ++++++++++++++++++++++---------
> 1 file changed, 37 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index b2afd2b6fbca..53b8c1a68f90 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -1616,11 +1616,17 @@ static void mlx5_cvq_kick_handler(struct work_struct *work)
> mvdev = wqent->mvdev;
> ndev = to_mlx5_vdpa_ndev(mvdev);
> cvq = &mvdev->cvq;
> +
> + mutex_lock(&ndev->reslock);
> +
> + if (!(mvdev->status & VIRTIO_CONFIG_S_DRIVER_OK))
> + goto out;
> +
> if (!(ndev->mvdev.actual_features & BIT_ULL(VIRTIO_NET_F_CTRL_VQ)))
> - return;
> + goto out;
>
> if (!cvq->ready)
> - return;
> + goto out;
>
> while (true) {
> err = vringh_getdesc_iotlb(&cvq->vring, &cvq->riov, &cvq->wiov, &cvq->head,
> @@ -1658,6 +1664,9 @@ static void mlx5_cvq_kick_handler(struct work_struct *work)
> queue_work(mvdev->wq, &wqent->work);
> break;
> }
> +
> +out:
> + mutex_unlock(&ndev->reslock);
> }
>
> static void mlx5_vdpa_kick_vq(struct vdpa_device *vdev, u16 idx)
> @@ -2132,7 +2141,7 @@ static int mlx5_vdpa_change_map(struct mlx5_vdpa_dev *mvdev, struct vhost_iotlb
> goto err_mr;
>
> if (!(mvdev->status & VIRTIO_CONFIG_S_DRIVER_OK))
> - return 0;
> + goto err_mr;
>
> restore_channels_info(ndev);
> err = setup_driver(mvdev);
> @@ -2147,12 +2156,14 @@ static int mlx5_vdpa_change_map(struct mlx5_vdpa_dev *mvdev, struct vhost_iotlb
> return err;
> }
>
> +/* reslock must be held for this function */
> static int setup_driver(struct mlx5_vdpa_dev *mvdev)
> {
> struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
> int err;
>
> - mutex_lock(&ndev->reslock);
> + WARN_ON(!mutex_is_locked(&ndev->reslock));
> +
> if (ndev->setup) {
> mlx5_vdpa_warn(mvdev, "setup driver called for already setup driver\n");
> err = 0;
> @@ -2182,7 +2193,6 @@ static int setup_driver(struct mlx5_vdpa_dev *mvdev)
> goto err_fwd;
> }
> ndev->setup = true;
> - mutex_unlock(&ndev->reslock);
>
> return 0;
>
> @@ -2193,23 +2203,23 @@ static int setup_driver(struct mlx5_vdpa_dev *mvdev)
> err_rqt:
> teardown_virtqueues(ndev);
> out:
> - mutex_unlock(&ndev->reslock);
> return err;
> }
>
> +/* reslock must be held for this function */
> static void teardown_driver(struct mlx5_vdpa_net *ndev)
> {
> - mutex_lock(&ndev->reslock);
> +
> + WARN_ON(!mutex_is_locked(&ndev->reslock));
> +
> if (!ndev->setup)
> - goto out;
> + return;
>
> remove_fwd_to_tir(ndev);
> destroy_tir(ndev);
> destroy_rqt(ndev);
> teardown_virtqueues(ndev);
> ndev->setup = false;
> -out:
> - mutex_unlock(&ndev->reslock);
> }
>
> static void clear_vqs_ready(struct mlx5_vdpa_net *ndev)
> @@ -2230,6 +2240,8 @@ static void mlx5_vdpa_set_status(struct vdpa_device *vdev, u8 status)
>
> print_status(mvdev, status, true);
>
> + mutex_lock(&ndev->reslock);
> +
> if ((status ^ ndev->mvdev.status) & VIRTIO_CONFIG_S_DRIVER_OK) {
> if (status & VIRTIO_CONFIG_S_DRIVER_OK) {
> err = setup_driver(mvdev);
> @@ -2239,16 +2251,19 @@ static void mlx5_vdpa_set_status(struct vdpa_device *vdev, u8 status)
> }
> } else {
> mlx5_vdpa_warn(mvdev, "did not expect DRIVER_OK to be cleared\n");
> - return;
> + goto err_clear;
> }
> }
>
> ndev->mvdev.status = status;
> + mutex_unlock(&ndev->reslock);
> return;
>
> err_setup:
> mlx5_vdpa_destroy_mr(&ndev->mvdev);
> ndev->mvdev.status |= VIRTIO_CONFIG_S_FAILED;
> +err_clear:
> + mutex_unlock(&ndev->reslock);
> }
>
> static int mlx5_vdpa_reset(struct vdpa_device *vdev)
> @@ -2258,6 +2273,8 @@ static int mlx5_vdpa_reset(struct vdpa_device *vdev)
>
> print_status(mvdev, 0, true);
> mlx5_vdpa_info(mvdev, "performing device reset\n");
> +
> + mutex_lock(&ndev->reslock);
> teardown_driver(ndev);
> clear_vqs_ready(ndev);
> mlx5_vdpa_destroy_mr(&ndev->mvdev);
> @@ -2270,6 +2287,7 @@ static int mlx5_vdpa_reset(struct vdpa_device *vdev)
> if (mlx5_vdpa_create_mr(mvdev, NULL))
> mlx5_vdpa_warn(mvdev, "create MR failed\n");
> }
> + mutex_unlock(&ndev->reslock);
>
> return 0;
> }
> @@ -2305,19 +2323,24 @@ static u32 mlx5_vdpa_get_generation(struct vdpa_device *vdev)
> static int mlx5_vdpa_set_map(struct vdpa_device *vdev, struct vhost_iotlb *iotlb)
> {
> struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
> + struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
> bool change_map;
> int err;
>
> + mutex_lock(&ndev->reslock);
> +
> err = mlx5_vdpa_handle_set_map(mvdev, iotlb, &change_map);
> if (err) {
> mlx5_vdpa_warn(mvdev, "set map failed(%d)\n", err);
> - return err;
> + goto err;
> }
>
> if (change_map)
> - return mlx5_vdpa_change_map(mvdev, iotlb);
> + err = mlx5_vdpa_change_map(mvdev, iotlb);
>
> - return 0;
> +err:
> + mutex_unlock(&ndev->reslock);
> + return err;
> }
>
> static void mlx5_vdpa_free(struct vdpa_device *vdev)
> --
> 2.18.1
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