Re: [dpdk-dev] [PATCH v3 02/21] net/virtio: vring init for packed queues

[Tiwei Bie <tiwei.bie@intel.com>]

On Thu, Apr 05, 2018 at 12:10:12PM +0200, Jens Freimann wrote:
> Add and initialize descriptor data structures.
> 
> Signed-off-by: Jens Freimann <jfreimann@redhat.com>
> ---
[...]
> diff --git a/drivers/net/virtio/virtio_ring.h b/drivers/net/virtio/virtio_ring.h
> index 9e3c2a015..1bd7ba98e 100644
> --- a/drivers/net/virtio/virtio_ring.h
> +++ b/drivers/net/virtio/virtio_ring.h
> @@ -9,6 +9,7 @@
>  
>  #include <rte_common.h>
>  
> +

There is no need to add this empty line.

>  /* This marks a buffer as continuing via the next field. */
>  #define VRING_DESC_F_NEXT       1
>  /* This marks a buffer as write-only (otherwise read-only). */
> @@ -54,11 +55,38 @@ struct vring_used {
>  	struct vring_used_elem ring[0];
>  };
>  
> +/* For support of packed virtqueues in Virtio 1.1 the format of descriptors
> + * looks like this.
> + */
> +struct vring_desc_packed {
> +	uint64_t addr;
> +	uint32_t len;
> +	uint16_t index;
> +	uint16_t flags;
> +};
> +
> +#define RING_EVENT_FLAGS_ENABLE 0x0
> +#define RING_EVENT_FLAGS_DISABLE 0x1
> +#define RING_EVENT_FLAGS_DESC 0x2
> +struct vring_packed_desc_event {
> +	uint16_t desc_event_off_wrap;
> +	uint16_t desc_event_flags;
> +};
> +
>  struct vring {
>  	unsigned int num;
> -	struct vring_desc  *desc;
> -	struct vring_avail *avail;
> -	struct vring_used  *used;
> +	union {
> +		struct vring_desc_packed *desc_packed;
> +		struct vring_desc *desc;
> +	};
> +	union {
> +		struct vring_avail *avail;
> +		struct vring_packed_desc_event *driver_event;
> +	};
> +	union {
> +		struct vring_used  *used;
> +		struct vring_packed_desc_event *device_event;
> +	};
>  };
>  
>  /* The standard layout for the ring is a continuous chunk of memory which
> @@ -95,10 +123,16 @@ struct vring {
>  #define vring_avail_event(vr) (*(uint16_t *)&(vr)->used->ring[(vr)->num])
>  
>  static inline size_t
> -vring_size(unsigned int num, unsigned long align)
> +vring_size(struct virtio_hw *hw, unsigned int num, unsigned long align)
>  {
>  	size_t size;
>  
> +	if (vtpci_packed_queue(hw)) {
> +		size = num * sizeof(struct vring_desc_packed);

I think you need to add paddings based on the alignment.

> +		size += 2 * sizeof(struct vring_packed_desc_event);
> +		return size;
> +	}
> +
>  	size = num * sizeof(struct vring_desc);
>  	size += sizeof(struct vring_avail) + (num * sizeof(uint16_t));
>  	size = RTE_ALIGN_CEIL(size, align);
> @@ -108,10 +142,19 @@ vring_size(unsigned int num, unsigned long align)
>  }
>  
>  static inline void
> -vring_init(struct vring *vr, unsigned int num, uint8_t *p,
> +vring_init(struct virtio_hw *hw, struct vring *vr, unsigned int num, uint8_t *p,
>  	unsigned long align)
>  {
>  	vr->num = num;
> +	if (vtpci_packed_queue(hw)) {
> +		vr->desc_packed = (struct vring_desc_packed *)p;
> +		vr->driver_event = (struct vring_packed_desc_event *) (p +
> +			num * sizeof(struct vring_desc_packed));

I think paddings are needed here.

> +		vr->device_event = (struct vring_packed_desc_event *) (vr->driver_event +
> +			sizeof(struct vring_packed_desc_event));
> +		return;
> +	}
> +
>  	vr->desc = (struct vring_desc *) p;
>  	vr->avail = (struct vring_avail *) (p +
>  		num * sizeof(struct vring_desc));
> diff --git a/drivers/net/virtio/virtqueue.h b/drivers/net/virtio/virtqueue.h
> index 14364f356..cc2e7c0f6 100644
> --- a/drivers/net/virtio/virtqueue.h
> +++ b/drivers/net/virtio/virtqueue.h
> @@ -245,6 +245,16 @@ struct virtio_tx_region {
>  			   __attribute__((__aligned__(16)));
>  };
>  
> +static inline void
> +vring_desc_init_packed(struct vring *vr, int n)
> +{
> +	int i;
> +	for (i = 0; i < n; i++) {
> +		struct vring_desc_packed *desc = &vr->desc_packed[i];
> +		desc->index = i;
> +	}
> +}
> +
>  /* Chain all the descriptors in the ring with an END */
>  static inline void
>  vring_desc_init(struct vring_desc *dp, uint16_t n)
> -- 
> 2.14.3
>