Re: [PATCH v2] vdpa/mlx5: Support interrupt bypassing

* Re: [PATCH v2] vdpa/mlx5: Support interrupt bypassing
       [not found] <20230417083517.134528-1-elic@nvidia.com>
@ 2023-04-19  4:39 ` Jason Wang
  2023-04-21  6:54   ` Michael S. Tsirkin
  0 siblings, 1 reply; 3+ messages in thread
From: Jason Wang @ 2023-04-19  4:39 UTC (permalink / raw)
  To: Eli Cohen; +Cc: parav, mst, virtualization, eperezma, Saeed Mahameed

On Mon, Apr 17, 2023 at 4:35 PM Eli Cohen <elic@nvidia.com> wrote:
>
> Add support for generation of interrupts from the device directly to the
> VM to the VCPU thus avoiding the overhead on the host CPU.
>
> When supported, the driver will attempt to allocate vectors for each
> data virtqueue. If a vector for a virtqueue cannot be provided it will
> use the QP mode where notifications go through the driver.
>
> In addition, we add a shutdown callback to make sure allocated
> interrupts are released in case of shutdown to allow clean shutdown.
>
> Issue: 2211199
> Change-Id: I7633ee56ca2861a8d0f4935bb29109c8e80f352c
> Signed-off-by: Eli Cohen <elic@nvidia.com>
> Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
> ---
> v1 -> v2:
> 1. Remove parentheses around return statement
> 2. Immediately return if vector entry found
> 3. Use boolean instead of counter on used entry tracking
> 4. Fix symmetry in teardown_vq()
>
> This patch is still under discussion but I wanted to address commnents
> and have this is the basis for further discussion.
>
>  drivers/vdpa/mlx5/net/mlx5_vnet.c | 140 ++++++++++++++++++++++++++++--
>  drivers/vdpa/mlx5/net/mlx5_vnet.h |  14 +++
>  2 files changed, 145 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index e29e32b306ad..2360c643148f 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -83,6 +83,7 @@ struct mlx5_vq_restore_info {
>         u64 driver_addr;
>         u16 avail_index;
>         u16 used_index;
> +       struct msi_map map;
>         bool ready;
>         bool restore;
>  };
> @@ -118,6 +119,7 @@ struct mlx5_vdpa_virtqueue {
>         u16 avail_idx;
>         u16 used_idx;
>         int fw_state;
> +       struct msi_map map;
>
>         /* keep last in the struct */
>         struct mlx5_vq_restore_info ri;
> @@ -808,6 +810,13 @@ static bool counters_supported(const struct mlx5_vdpa_dev *mvdev)
>                BIT_ULL(MLX5_OBJ_TYPE_VIRTIO_Q_COUNTERS);
>  }
>
> +static bool msix_mode_supported(struct mlx5_vdpa_dev *mvdev)
> +{
> +       return MLX5_CAP_DEV_VDPA_EMULATION(mvdev->mdev, event_mode) &
> +               (1 << MLX5_VIRTIO_Q_EVENT_MODE_MSIX_MODE) &&
> +               pci_msix_can_alloc_dyn(mvdev->mdev->pdev);
> +}
> +
>  static int create_virtqueue(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *mvq)
>  {
>         int inlen = MLX5_ST_SZ_BYTES(create_virtio_net_q_in);
> @@ -849,9 +858,15 @@ static int create_virtqueue(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtque
>         if (vq_is_tx(mvq->index))
>                 MLX5_SET(virtio_net_q_object, obj_context, tisn_or_qpn, ndev->res.tisn);
>
> -       MLX5_SET(virtio_q, vq_ctx, event_mode, MLX5_VIRTIO_Q_EVENT_MODE_QP_MODE);
> +       if (mvq->map.virq) {
> +               MLX5_SET(virtio_q, vq_ctx, event_mode, MLX5_VIRTIO_Q_EVENT_MODE_MSIX_MODE);
> +               MLX5_SET(virtio_q, vq_ctx, event_qpn_or_msix, mvq->map.index);
> +       } else {
> +               MLX5_SET(virtio_q, vq_ctx, event_mode, MLX5_VIRTIO_Q_EVENT_MODE_QP_MODE);
> +               MLX5_SET(virtio_q, vq_ctx, event_qpn_or_msix, mvq->fwqp.mqp.qpn);
> +       }
> +
>         MLX5_SET(virtio_q, vq_ctx, queue_index, mvq->index);
> -       MLX5_SET(virtio_q, vq_ctx, event_qpn_or_msix, mvq->fwqp.mqp.qpn);
>         MLX5_SET(virtio_q, vq_ctx, queue_size, mvq->num_ent);
>         MLX5_SET(virtio_q, vq_ctx, virtio_version_1_0,
>                  !!(ndev->mvdev.actual_features & BIT_ULL(VIRTIO_F_VERSION_1)));
> @@ -1194,6 +1209,34 @@ static void counter_set_dealloc(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_vir
>                 mlx5_vdpa_warn(&ndev->mvdev, "dealloc counter set 0x%x\n", mvq->counter_set_id);
>  }
>
> +static void alloc_vector(struct mlx5_vdpa_net *ndev,
> +                        struct mlx5_vdpa_virtqueue *mvq)
> +{
> +       struct mlx5_vdpa_irq_pool *irqp = &ndev->irqp;
> +       int i;
> +
> +       for (i = 0; i < irqp->num_ent; i++) {
> +               if (!irqp->entries[i].used) {
> +                       irqp->entries[i].used = true;
> +                       mvq->map = irqp->entries[i].map;
> +                       return;
> +               }
> +       }
> +}
> +
> +static void dealloc_vector(struct mlx5_vdpa_net *ndev,
> +                          struct mlx5_vdpa_virtqueue *mvq)
> +{
> +       struct mlx5_vdpa_irq_pool *irqp = &ndev->irqp;
> +       int i;
> +
> +       for (i = 0; i < irqp->num_ent; i++)
> +               if (mvq->map.virq == irqp->entries[i].map.virq) {
> +                       irqp->entries[i].used = false;
> +                       return;
> +               }
> +}
> +
>  static int setup_vq(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *mvq)
>  {
>         u16 idx = mvq->index;
> @@ -1223,27 +1266,31 @@ static int setup_vq(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *mvq)
>
>         err = counter_set_alloc(ndev, mvq);
>         if (err)
> -               goto err_counter;
> +               goto err_connect;
>
> +       alloc_vector(ndev, mvq);
>         err = create_virtqueue(ndev, mvq);
>         if (err)
> -               goto err_connect;
> +               goto err_vq;
>
>         if (mvq->ready) {
>                 err = modify_virtqueue(ndev, mvq, MLX5_VIRTIO_NET_Q_OBJECT_STATE_RDY);
>                 if (err) {
>                         mlx5_vdpa_warn(&ndev->mvdev, "failed to modify to ready vq idx %d(%d)\n",
>                                        idx, err);
> -                       goto err_connect;
> +                       goto err_modify;
>                 }
>         }
>
>         mvq->initialized = true;
>         return 0;
>
> -err_connect:
> +err_modify:
> +       destroy_virtqueue(ndev, mvq);
> +err_vq:
> +       dealloc_vector(ndev, mvq);
>         counter_set_dealloc(ndev, mvq);
> -err_counter:
> +err_connect:
>         qp_destroy(ndev, &mvq->vqqp);
>  err_vqqp:
>         qp_destroy(ndev, &mvq->fwqp);
> @@ -1288,6 +1335,7 @@ static void teardown_vq(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *
>
>         suspend_vq(ndev, mvq);
>         destroy_virtqueue(ndev, mvq);
> +       dealloc_vector(ndev, mvq);
>         counter_set_dealloc(ndev, mvq);
>         qp_destroy(ndev, &mvq->vqqp);
>         qp_destroy(ndev, &mvq->fwqp);
> @@ -2505,6 +2553,7 @@ static int save_channel_info(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqu
>         ri->desc_addr = mvq->desc_addr;
>         ri->device_addr = mvq->device_addr;
>         ri->driver_addr = mvq->driver_addr;
> +       ri->map = mvq->map;
>         ri->restore = true;
>         return 0;
>  }
> @@ -2549,6 +2598,7 @@ static void restore_channels_info(struct mlx5_vdpa_net *ndev)
>                 mvq->desc_addr = ri->desc_addr;
>                 mvq->device_addr = ri->device_addr;
>                 mvq->driver_addr = ri->driver_addr;
> +               mvq->map = ri->map;
>         }
>  }
>
> @@ -2833,6 +2883,21 @@ static struct device *mlx5_get_vq_dma_dev(struct vdpa_device *vdev, u16 idx)
>         return mvdev->vdev.dma_dev;
>  }
>
> +static void free_irqs(struct mlx5_vdpa_net *ndev)
> +{
> +       struct mlx5_vdpa_irq_pool_entry *ent;
> +       int i;
> +
> +       if (!msix_mode_supported(&ndev->mvdev))
> +               return;
> +
> +       for (i = ndev->irqp.num_ent - 1; i >= 0; i--) {
> +               ent = ndev->irqp.entries + i;
> +               mlx5_msix_free(ndev->mvdev.mdev, ent->map);
> +       }
> +       kfree(ndev->irqp.entries);
> +}
> +
>  static void mlx5_vdpa_free(struct vdpa_device *vdev)
>  {
>         struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
> @@ -2848,6 +2913,7 @@ static void mlx5_vdpa_free(struct vdpa_device *vdev)
>                 mlx5_mpfs_del_mac(pfmdev, ndev->config.mac);
>         }
>         mlx5_vdpa_free_resources(&ndev->mvdev);
> +       free_irqs(ndev);
>         kfree(ndev->event_cbs);
>         kfree(ndev->vqs);
>  }
> @@ -2876,9 +2942,23 @@ static struct vdpa_notification_area mlx5_get_vq_notification(struct vdpa_device
>         return ret;
>  }
>
> -static int mlx5_get_vq_irq(struct vdpa_device *vdv, u16 idx)
> +static int mlx5_get_vq_irq(struct vdpa_device *vdev, u16 idx)
>  {
> -       return -EOPNOTSUPP;
> +       struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
> +       struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
> +       struct mlx5_vdpa_virtqueue *mvq;
> +
> +       if (!is_index_valid(mvdev, idx))
> +               return -EINVAL;
> +
> +       if (is_ctrl_vq_idx(mvdev, idx))
> +               return -EOPNOTSUPP;
> +
> +       mvq = &ndev->vqs[idx];
> +       if (!mvq->map.virq)
> +               return -EOPNOTSUPP;
> +
> +       return mvq->map.virq;
>  }
>
>  static u64 mlx5_vdpa_get_driver_features(struct vdpa_device *vdev)
> @@ -3155,6 +3235,35 @@ static int config_func_mtu(struct mlx5_core_dev *mdev, u16 mtu)
>         return err;
>  }
>
> +static irqreturn_t int_handler(int irq, void *nh)
> +{
> +       return IRQ_HANDLED;
> +}

I still don't understand when this handler will be called.

E.g IFCVF did:

static irqreturn_t ifcvf_vq_intr_handler(int irq, void *arg)
{
        struct vring_info *vring = arg;

        if (vring->cb.callback)
                return vring->cb.callback(vring->cb.private);

        return IRQ_HANDLED;
}

So when the irq bypass doesn't work it will fall back to a slow path.

Maybe some comments here or changelog would be helpful.

Thanks

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