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From: Jason Wang <jasowang@redhat.com>
To: Si-Wei Liu <si-wei.liu@oracle.com>, mst@redhat.com, elic@nvidia.com
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	virtualization@lists.linux-foundation.org
Subject: Re: [PATCH 3/3] mlx5_vdpa: defer clear_virtqueues to until DRIVER_OK
Date: Tue, 9 Feb 2021 11:37:22 +0800	[thread overview]
Message-ID: <2e2bc8d7-5d64-c28c-9aa0-1df32c7dcef3@redhat.com> (raw)
In-Reply-To: <1612614564-4220-3-git-send-email-si-wei.liu@oracle.com>


On 2021/2/6 下午8:29, Si-Wei Liu wrote:
> While virtq is stopped,  get_vq_state() is supposed to
> be  called to  get  sync'ed  with  the latest internal
> avail_index from device. The saved avail_index is used
> to restate  the virtq  once device is started.  Commit
> b35ccebe3ef7 introduced the clear_virtqueues() routine
> to  reset  the saved  avail_index,  however, the index
> gets cleared a bit earlier before get_vq_state() tries
> to read it. This would cause consistency problems when
> virtq is restarted, e.g. through a series of link down
> and link up events. We  could  defer  the  clearing of
> avail_index  to  until  the  device  is to be started,
> i.e. until  VIRTIO_CONFIG_S_DRIVER_OK  is set again in
> set_status().
>
> Fixes: b35ccebe3ef7 ("vdpa/mlx5: Restore the hardware used index after change map")
> Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
> ---
>   drivers/vdpa/mlx5/net/mlx5_vnet.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index aa6f8cd..444ab58 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -1785,7 +1785,6 @@ static void mlx5_vdpa_set_status(struct vdpa_device *vdev, u8 status)
>   	if (!status) {
>   		mlx5_vdpa_info(mvdev, "performing device reset\n");
>   		teardown_driver(ndev);
> -		clear_virtqueues(ndev);
>   		mlx5_vdpa_destroy_mr(&ndev->mvdev);
>   		ndev->mvdev.status = 0;
>   		++mvdev->generation;
> @@ -1794,6 +1793,7 @@ static void mlx5_vdpa_set_status(struct vdpa_device *vdev, u8 status)
>   
>   	if ((status ^ ndev->mvdev.status) & VIRTIO_CONFIG_S_DRIVER_OK) {
>   		if (status & VIRTIO_CONFIG_S_DRIVER_OK) {
> +			clear_virtqueues(ndev);


Rethink about this. As mentioned in another thread, this in fact breaks 
set_vq_state().  (See vhost_virtqueue_start() -> 
vhost_vdpa_set_vring_base() in qemu codes).

The issue is that the avail idx is forgot, we need keep it.

Thanks


>   			err = setup_driver(ndev);
>   			if (err) {
>   				mlx5_vdpa_warn(mvdev, "failed to setup driver\n");

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WARNING: multiple messages have this Message-ID (diff)
From: Jason Wang <jasowang@redhat.com>
To: Si-Wei Liu <si-wei.liu@oracle.com>, mst@redhat.com, elic@nvidia.com
Cc: linux-kernel@vger.kernel.org,
	virtualization@lists.linux-foundation.org,
	netdev@vger.kernel.org
Subject: Re: [PATCH 3/3] mlx5_vdpa: defer clear_virtqueues to until DRIVER_OK
Date: Tue, 9 Feb 2021 11:37:22 +0800	[thread overview]
Message-ID: <2e2bc8d7-5d64-c28c-9aa0-1df32c7dcef3@redhat.com> (raw)
In-Reply-To: <1612614564-4220-3-git-send-email-si-wei.liu@oracle.com>


On 2021/2/6 下午8:29, Si-Wei Liu wrote:
> While virtq is stopped,  get_vq_state() is supposed to
> be  called to  get  sync'ed  with  the latest internal
> avail_index from device. The saved avail_index is used
> to restate  the virtq  once device is started.  Commit
> b35ccebe3ef7 introduced the clear_virtqueues() routine
> to  reset  the saved  avail_index,  however, the index
> gets cleared a bit earlier before get_vq_state() tries
> to read it. This would cause consistency problems when
> virtq is restarted, e.g. through a series of link down
> and link up events. We  could  defer  the  clearing of
> avail_index  to  until  the  device  is to be started,
> i.e. until  VIRTIO_CONFIG_S_DRIVER_OK  is set again in
> set_status().
>
> Fixes: b35ccebe3ef7 ("vdpa/mlx5: Restore the hardware used index after change map")
> Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
> ---
>   drivers/vdpa/mlx5/net/mlx5_vnet.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index aa6f8cd..444ab58 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -1785,7 +1785,6 @@ static void mlx5_vdpa_set_status(struct vdpa_device *vdev, u8 status)
>   	if (!status) {
>   		mlx5_vdpa_info(mvdev, "performing device reset\n");
>   		teardown_driver(ndev);
> -		clear_virtqueues(ndev);
>   		mlx5_vdpa_destroy_mr(&ndev->mvdev);
>   		ndev->mvdev.status = 0;
>   		++mvdev->generation;
> @@ -1794,6 +1793,7 @@ static void mlx5_vdpa_set_status(struct vdpa_device *vdev, u8 status)
>   
>   	if ((status ^ ndev->mvdev.status) & VIRTIO_CONFIG_S_DRIVER_OK) {
>   		if (status & VIRTIO_CONFIG_S_DRIVER_OK) {
> +			clear_virtqueues(ndev);


Rethink about this. As mentioned in another thread, this in fact breaks 
set_vq_state().  (See vhost_virtqueue_start() -> 
vhost_vdpa_set_vring_base() in qemu codes).

The issue is that the avail idx is forgot, we need keep it.

Thanks


>   			err = setup_driver(ndev);
>   			if (err) {
>   				mlx5_vdpa_warn(mvdev, "failed to setup driver\n");


  parent reply	other threads:[~2021-02-09  3:44 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-06 12:29 [PATCH 1/3] mlx5_vdpa: should exclude header length and fcs from mtu Si-Wei Liu
2021-02-06 12:29 ` Si-Wei Liu
2021-02-06 12:29 ` [PATCH 2/3] mlx5_vdpa: fix feature negotiation across device reset Si-Wei Liu
2021-02-06 12:29   ` Si-Wei Liu
2021-02-08  4:37   ` Jason Wang
2021-02-08  4:37     ` Jason Wang
2021-02-08  5:35   ` Eli Cohen
2021-02-09  1:20     ` Si-Wei Liu
2021-02-09  1:20       ` Si-Wei Liu
2021-02-10 12:28       ` Michael S. Tsirkin
2021-02-10 12:28         ` Michael S. Tsirkin
2021-02-06 12:29 ` [PATCH 3/3] mlx5_vdpa: defer clear_virtqueues to until DRIVER_OK Si-Wei Liu
2021-02-06 12:29   ` Si-Wei Liu
2021-02-08  4:38   ` Jason Wang
2021-02-08  4:38     ` Jason Wang
2021-02-08  5:48   ` Eli Cohen
2021-02-09  1:40     ` Si-Wei Liu
2021-02-09  1:40       ` Si-Wei Liu
2021-02-09  3:37   ` Jason Wang [this message]
2021-02-09  3:37     ` Jason Wang
2021-02-10  0:26     ` Si-Wei Liu
2021-02-10  0:26       ` Si-Wei Liu
2021-02-10  4:00       ` Jason Wang
2021-02-10  4:00         ` Jason Wang
2021-02-08  4:38 ` [PATCH 1/3] mlx5_vdpa: should exclude header length and fcs from mtu Jason Wang
2021-02-08  4:38   ` Jason Wang
2021-02-08  5:35 ` Eli Cohen

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