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Date: Mon, 8 Feb 2021 12:27:18 +0800
From: Jason Wang <jasowang@...hat.com>
To: Si-Wei Liu <si-wei.liu@...cle.com>, Eli Cohen <elic@...dia.com>,
mst@...hat.com, virtualization@...ts.linux-foundation.org,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: lulu@...hat.com
Subject: Re: [PATCH v1] vdpa/mlx5: Restore the hardware used index after
change map
On 2021/2/6 上午7:07, Si-Wei Liu wrote:
>
>
> On 2/3/2021 11:36 PM, Eli Cohen wrote:
>> When a change of memory map occurs, the hardware resources are destroyed
>> and then re-created again with the new memory map. In such case, we need
>> to restore the hardware available and used indices. The driver failed to
>> restore the used index which is added here.
>>
>> Also, since the driver also fails to reset the available and used
>> indices upon device reset, fix this here to avoid regression caused by
>> the fact that used index may not be zero upon device reset.
>>
>> Fixes: 1a86b377aa21 ("vdpa/mlx5: Add VDPA driver for supported mlx5
>> devices")
>> Signed-off-by: Eli Cohen <elic@...dia.com>
>> ---
>> v0 -> v1:
>> Clear indices upon device reset
>>
>> drivers/vdpa/mlx5/net/mlx5_vnet.c | 18 ++++++++++++++++++
>> 1 file changed, 18 insertions(+)
>>
>> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c
>> b/drivers/vdpa/mlx5/net/mlx5_vnet.c
>> index 88dde3455bfd..b5fe6d2ad22f 100644
>> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
>> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
>> @@ -87,6 +87,7 @@ struct mlx5_vq_restore_info {
>> u64 device_addr;
>> u64 driver_addr;
>> u16 avail_index;
>> + u16 used_index;
>> bool ready;
>> struct vdpa_callback cb;
>> bool restore;
>> @@ -121,6 +122,7 @@ struct mlx5_vdpa_virtqueue {
>> u32 virtq_id;
>> struct mlx5_vdpa_net *ndev;
>> u16 avail_idx;
>> + u16 used_idx;
>> int fw_state;
>> /* keep last in the struct */
>> @@ -804,6 +806,7 @@ static int create_virtqueue(struct mlx5_vdpa_net
>> *ndev, struct mlx5_vdpa_virtque
>> obj_context = MLX5_ADDR_OF(create_virtio_net_q_in, in,
>> obj_context);
>> MLX5_SET(virtio_net_q_object, obj_context, hw_available_index,
>> mvq->avail_idx);
>> + MLX5_SET(virtio_net_q_object, obj_context, hw_used_index,
>> mvq->used_idx);
>> MLX5_SET(virtio_net_q_object, obj_context,
>> queue_feature_bit_mask_12_3,
>> get_features_12_3(ndev->mvdev.actual_features));
>> vq_ctx = MLX5_ADDR_OF(virtio_net_q_object, obj_context,
>> virtio_q_context);
>> @@ -1022,6 +1025,7 @@ static int connect_qps(struct mlx5_vdpa_net
>> *ndev, struct mlx5_vdpa_virtqueue *m
>> struct mlx5_virtq_attr {
>> u8 state;
>> u16 available_index;
>> + u16 used_index;
>> };
>> static int query_virtqueue(struct mlx5_vdpa_net *ndev, struct
>> mlx5_vdpa_virtqueue *mvq,
>> @@ -1052,6 +1056,7 @@ static int query_virtqueue(struct mlx5_vdpa_net
>> *ndev, struct mlx5_vdpa_virtqueu
>> memset(attr, 0, sizeof(*attr));
>> attr->state = MLX5_GET(virtio_net_q_object, obj_context, state);
>> attr->available_index = MLX5_GET(virtio_net_q_object,
>> obj_context, hw_available_index);
>> + attr->used_index = MLX5_GET(virtio_net_q_object, obj_context,
>> hw_used_index);
>> kfree(out);
>> return 0;
>> @@ -1535,6 +1540,16 @@ static void teardown_virtqueues(struct
>> mlx5_vdpa_net *ndev)
>> }
>> }
>> +static void clear_virtqueues(struct mlx5_vdpa_net *ndev)
>> +{
>> + int i;
>> +
>> + for (i = ndev->mvdev.max_vqs - 1; i >= 0; i--) {
>> + ndev->vqs[i].avail_idx = 0;
>> + ndev->vqs[i].used_idx = 0;
>> + }
>> +}
>> +
>> /* TODO: cross-endian support */
>> static inline bool mlx5_vdpa_is_little_endian(struct mlx5_vdpa_dev
>> *mvdev)
>> {
>> @@ -1610,6 +1625,7 @@ static int save_channel_info(struct
>> mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqu
>> return err;
>> ri->avail_index = attr.available_index;
>> + ri->used_index = attr.used_index;
>> ri->ready = mvq->ready;
>> ri->num_ent = mvq->num_ent;
>> ri->desc_addr = mvq->desc_addr;
>> @@ -1654,6 +1670,7 @@ static void restore_channels_info(struct
>> mlx5_vdpa_net *ndev)
>> continue;
>> mvq->avail_idx = ri->avail_index;
>> + mvq->used_idx = ri->used_index;
>> mvq->ready = ri->ready;
>> mvq->num_ent = ri->num_ent;
>> mvq->desc_addr = ri->desc_addr;
>> @@ -1768,6 +1785,7 @@ 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);
> The clearing looks fine at the first glance, as it aligns with the
> other state cleanups floating around at the same place. However, the
> thing is get_vq_state() is supposed to be called right after to get
> sync'ed with the latest internal avail_index from device while vq is
> stopped. The index was saved in the driver software at vq suspension,
> but before the virtq object is destroyed. We shouldn't clear the
> avail_index too early.
Good point.
There's a limitation on the virtio spec and vDPA framework that we can
not simply differ device suspending from device reset.
Need to think about that. I suggest a new state in [1], the issue is
that people doesn't like the asynchronous API that it introduces.
>
> Possibly it can be postponed to where VIRTIO_CONFIG_S_DRIVER_OK gets
> set again, i.e. right before the setup_driver() in
> mlx5_vdpa_set_status()?
Looks like a good workaround.
Thanks
>
> -Siwei
[1]
https://lists.oasis-open.org/archives/virtio-comment/202012/msg00029.html
>
>> mlx5_vdpa_destroy_mr(&ndev->mvdev);
>> ndev->mvdev.status = 0;
>> ndev->mvdev.mlx_features = 0;
>
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