Re: [PATCH 1/1] vdpa/mlx5: Support interrupt bypassing

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Apr 03, 2023 at 07:20:39PM +0300, Eli Cohen 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.
> 
> Signed-off-by: Eli Cohen <elic@nvidia.com>
> Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
> ---
>  drivers/vdpa/mlx5/net/mlx5_vnet.c | 139 ++++++++++++++++++++++++++++--
>  drivers/vdpa/mlx5/net/mlx5_vnet.h |  14 +++
>  2 files changed, 144 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index 520646ae7fa0..215a46cf8a98 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;
> @@ -792,6 +794,13 @@ 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));

Don't add () around return value. too many () just obscures the logic.


> +}
> +
>  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);
> @@ -829,9 +838,15 @@ 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)));
> @@ -1174,6 +1189,32 @@ 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].usecount) {
> +			irqp->entries[i].usecount++;
> +			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].usecount--;
> +}
> +
>  static int setup_vq(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *mvq)
>  {
>  	u16 idx = mvq->index;
> @@ -1203,27 +1244,31 @@ 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);
> @@ -1267,6 +1312,7 @@ static void teardown_vq(struct mlx5_vdpa_net *ndev, struct mlx5_vdpa_virtqueue *
>  		return;
>  
>  	suspend_vq(ndev, mvq);
> +	dealloc_vector(ndev, mvq);
>  	destroy_virtqueue(ndev, mvq);
>  	counter_set_dealloc(ndev, mvq);
>  	qp_destroy(ndev, &mvq->vqqp);
> @@ -2374,6 +2420,7 @@ 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;
>  }
> @@ -2418,6 +2465,7 @@ 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;
>  	}
>  }
>  
> @@ -2693,6 +2741,22 @@ 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);
> +		ndev->irqp.num_ent--;
> +	}
> +	kfree(ndev->irqp.entries);
> +}
> +
>  static void mlx5_vdpa_free(struct vdpa_device *vdev)
>  {
>  	struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
> @@ -2708,6 +2772,7 @@ 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);
>  }
> @@ -2736,9 +2801,23 @@ 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)
> @@ -3095,6 +3174,35 @@ 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;
> +}
> +
> +static void allocate_irqs(struct mlx5_vdpa_net *ndev)
> +{
> +	struct mlx5_vdpa_irq_pool_entry *ent;
> +	int i;
> +
> +	if (!msix_mode_supported(&ndev->mvdev))
> +		return;
> +
> +	ndev->irqp.entries = kcalloc(ndev->mvdev.max_vqs, sizeof(*ndev->irqp.entries), GFP_KERNEL);
> +	if (!ndev->irqp.entries)
> +		return;
> +
> +	for (i = 0; i < ndev->mvdev.max_vqs; i++) {
> +		ent = ndev->irqp.entries + i;
> +		snprintf(ent->name, MLX5_VDPA_IRQ_NAME_LEN, "%s-vq-%d",
> +			 dev_name(&ndev->mvdev.vdev.dev), i);
> +		ent->map = mlx5_msix_alloc(ndev->mvdev.mdev, int_handler, NULL, ent->name);
> +		if (!ent->map.virq)
> +			return;
> +
> +		ndev->irqp.num_ent++;
> +	}
> +}
> +
>  static int mlx5_vdpa_dev_add(struct vdpa_mgmt_dev *v_mdev, const char *name,
>  			     const struct vdpa_dev_set_config *add_config)
>  {
> @@ -3171,6 +3279,7 @@ static int mlx5_vdpa_dev_add(struct vdpa_mgmt_dev *v_mdev, const char *name,
>  	}
>  
>  	init_mvqs(ndev);
> +	allocate_irqs(ndev);
>  	init_rwsem(&ndev->reslock);
>  	config = &ndev->config;
>  
> @@ -3358,6 +3467,17 @@ static void mlx5v_remove(struct auxiliary_device *adev)
>  	kfree(mgtdev);
>  }
>  
> +static void mlx5v_shutdown(struct auxiliary_device *auxdev)
> +{
> +	struct mlx5_vdpa_mgmtdev *mgtdev;
> +	struct mlx5_vdpa_net *ndev;
> +
> +	mgtdev = auxiliary_get_drvdata(auxdev);
> +	ndev = mgtdev->ndev;
> +
> +	free_irqs(ndev);
> +}
> +
>  static const struct auxiliary_device_id mlx5v_id_table[] = {
>  	{ .name = MLX5_ADEV_NAME ".vnet", },
>  	{},
> @@ -3369,6 +3489,7 @@ static struct auxiliary_driver mlx5v_driver = {
>  	.name = "vnet",
>  	.probe = mlx5v_probe,
>  	.remove = mlx5v_remove,
> +	.shutdown = mlx5v_shutdown,
>  	.id_table = mlx5v_id_table,
>  };
>  
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.h b/drivers/vdpa/mlx5/net/mlx5_vnet.h
> index c90a89e1de4d..e5063b310d3c 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.h
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.h
> @@ -26,6 +26,19 @@ static inline u16 key2vid(u64 key)
>  	return (u16)(key >> 48) & 0xfff;
>  }
>  
> +#define MLX5_VDPA_IRQ_NAME_LEN 32
> +
> +struct mlx5_vdpa_irq_pool_entry {
> +	struct msi_map map;
> +	int usecount;
> +	char name[MLX5_VDPA_IRQ_NAME_LEN];
> +};
> +
> +struct mlx5_vdpa_irq_pool {
> +	int num_ent;
> +	struct mlx5_vdpa_irq_pool_entry *entries;
> +};
> +
>  struct mlx5_vdpa_net {
>  	struct mlx5_vdpa_dev mvdev;
>  	struct mlx5_vdpa_net_resources res;
> @@ -49,6 +62,7 @@ struct mlx5_vdpa_net {
>  	struct vdpa_callback config_cb;
>  	struct mlx5_vdpa_wq_ent cvq_ent;
>  	struct hlist_head macvlan_hash[MLX5V_MACVLAN_SIZE];
> +	struct mlx5_vdpa_irq_pool irqp;
>  	struct dentry *debugfs;
>  };
>  
> -- 
> 2.39.2

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