RE: [PATCH RESEND V2 3/3] vdpa/mlx5: Use consistent RQT size

From: Eli Cohen
Date: Mon Apr 04 2022 - 07:07:46 EST

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> From: Michael S. Tsirkin <mst@xxxxxxxxxx>
> Sent: Monday, April 4, 2022 1:35 PM
> To: Jason Wang <jasowang@xxxxxxxxxx>
> Cc: Eli Cohen <elic@xxxxxxxxxx>; hdanton@xxxxxxxx; virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH RESEND V2 3/3] vdpa/mlx5: Use consistent RQT size
>
> On Tue, Mar 29, 2022 at 12:21:09PM +0800, Jason Wang wrote:
> > From: Eli Cohen <elic@xxxxxxxxxx>
> >
> > 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 addtion
>
> addition?

Do you need me to send another version?
If so, let's wait for Jason's reply.

>
> > 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")
> > Signed-off-by: Eli Cohen <elic@xxxxxxxxxx>
>
> Jason I don't have your ack or S.O.B on this one.
>
>
> > ---
> > 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 53b8c1a68f90..61bec1ed0bc9 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)
> > @@ -1582,7 +1560,7 @@ 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) {
> > @@ -1946,7 +1924,7 @@ 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;
> > @@ -2017,9 +1995,11 @@ 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;
> > @@ -2486,7 +2466,7 @@ 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;
> > @@ -2606,7 +2586,8 @@ 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",
> > @@ -2670,7 +2651,7 @@ 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)
> > @@ -2697,7 +2678,7 @@ 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;
> >
> > --
> > 2.18.1

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In reply to: Michael S. Tsirkin: "Re: [PATCH RESEND V2 3/3] vdpa/mlx5: Use consistent RQT size"
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