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

[Jens Freimann <jfreimann@redhat.com>]

On Thu, Apr 05, 2018 at 10:22:28PM +0800, Tiwei Bie wrote:
>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.

I'll align it with RTE_ALIGN_CEIL, like it's done for the used ring
address.

Thanks!

regards,
Jens 
>
>> +		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
>>