[SLOF] [PATCH v2 06/19] virtio-blk: add helpers for filling descriptors

[Thomas Huth]

On 20.01.2016 13:10, Nikunj A Dadhania wrote:
> Enable virtio_fill_desc/fill_blk_hdr with legacy and modern mode for
> further use
> 
> Signed-off-by: Nikunj A Dadhania <nikunj at linux.vnet.ibm.com>
> ---
>  lib/libvirtio/virtio-blk.c | 36 +++++++++++++++++++++---------------
>  lib/libvirtio/virtio.c     | 19 +++++++++++++++++++
>  lib/libvirtio/virtio.h     |  4 ++++
>  3 files changed, 44 insertions(+), 15 deletions(-)
> 
> diff --git a/lib/libvirtio/virtio-blk.c b/lib/libvirtio/virtio-blk.c
> index 1966721..8ae61bc 100644
> --- a/lib/libvirtio/virtio-blk.c
> +++ b/lib/libvirtio/virtio-blk.c
> @@ -13,6 +13,7 @@
>  #include <stdio.h>
>  #include <cpu.h>
>  #include <helpers.h>
> +#include <byteorder.h>
>  #include "virtio.h"
>  #include "virtio-blk.h"
>  
> @@ -82,6 +83,19 @@ virtioblk_shutdown(struct virtio_device *dev)
>  	virtio_reset_device(dev);
>  }
>  
> +static void fill_blk_hdr(struct virtio_blk_req *blkhdr, bool is_modern,
> +                         uint32_t type, uint32_t ioprio, uint32_t sector)
> +{
> +	if (is_modern) {
> +		blkhdr->type = cpu_to_le32(type);
> +		blkhdr->ioprio = cpu_to_le32(ioprio);
> +		blkhdr->sector = cpu_to_le64(sector);
> +	} else {
> +		blkhdr->type = type;
> +		blkhdr->ioprio = ioprio;
> +		blkhdr->sector = sector;
> +	}
> +}
>  
>  /**
>   * Read blocks
> @@ -137,33 +151,25 @@ virtioblk_read(struct virtio_device *dev, char *buf, long blocknum, long cnt)
>  	current_used_idx = &vq_used->idx;
>  
>  	/* Set up header */
> -	blkhdr.type = VIRTIO_BLK_T_IN | VIRTIO_BLK_T_BARRIER;
> -	blkhdr.ioprio = 1;
> -	blkhdr.sector = blocknum * blk_size / DEFAULT_SECTOR_SIZE;
> +	fill_blk_hdr(&blkhdr, false, VIRTIO_BLK_T_IN | VIRTIO_BLK_T_BARRIER,
> +		     1, blocknum * blk_size / DEFAULT_SECTOR_SIZE);

Do you need fill_blk_hdr in a later patch again so that it gets called
from another location, too? ... if not, I'd maybe fill in that code here
directly instead of creating a separate function for this.

>  	/* Determine descriptor index */
>  	id = (vq_avail->idx * 3) % vq_size;
>  
>  	/* Set up virtqueue descriptor for header */
>  	desc = &vq_desc[id];
> -	desc->addr = (uint64_t)&blkhdr;
> -	desc->len = sizeof(struct virtio_blk_req);
> -	desc->flags = VRING_DESC_F_NEXT;
> -	desc->next = (id + 1) % vq_size;
> +	virtio_fill_desc(desc, false, (uint64_t)&blkhdr, sizeof(struct virtio_blk_req),
> +		  VRING_DESC_F_NEXT, (id + 1) % vq_size);
>  
>  	/* Set up virtqueue descriptor for data */
>  	desc = &vq_desc[(id + 1) % vq_size];
> -	desc->addr = (uint64_t)buf;
> -	desc->len = cnt * blk_size;
> -	desc->flags = VRING_DESC_F_NEXT | VRING_DESC_F_WRITE;
> -	desc->next = (id + 2) % vq_size;
> +	virtio_fill_desc(desc, false, (uint64_t)buf, cnt * blk_size,
> +		  VRING_DESC_F_NEXT | VRING_DESC_F_WRITE, (id + 2) % vq_size);
>  
>  	/* Set up virtqueue descriptor for status */
>  	desc = &vq_desc[(id + 2) % vq_size];
> -	desc->addr = (uint64_t)&status;
> -	desc->len = 1;
> -	desc->flags = VRING_DESC_F_WRITE;
> -	desc->next = 0;
> +	virtio_fill_desc(desc, false, (uint64_t)&status, 1, VRING_DESC_F_WRITE, 0);
>  
>  	vq_avail->ring[vq_avail->idx % vq_size] = id;
>  	mb();
> diff --git a/lib/libvirtio/virtio.c b/lib/libvirtio/virtio.c
> index b5be2e4..3a75e44 100644
> --- a/lib/libvirtio/virtio.c
> +++ b/lib/libvirtio/virtio.c
> @@ -113,6 +113,25 @@ struct vring_used *virtio_get_vring_used(struct virtio_device *dev, int queue)
>  			       * sizeof(struct vring_avail));
>  }
>  
> +/**
> + * Fill the virtio ring descriptor depending on the legacy mode or virtio 1.0
> + */
> +void virtio_fill_desc(struct vring_desc *desc, bool is_modern,
> +                      uint64_t addr, uint32_t len,
> +                      uint16_t flags, uint16_t next)
> +{
> +	if (is_modern) {
> +		desc->addr = cpu_to_le64(addr);
> +		desc->len = cpu_to_le32(len);
> +		desc->flags = cpu_to_le16(flags);
> +		desc->next = cpu_to_le16(next);
> +	} else {
> +		desc->addr = addr;
> +		desc->len = len;
> +		desc->flags = flags;
> +		desc->next = next;
> +	}
> +}
>  
>  /**
>   * Reset virtio device
> diff --git a/lib/libvirtio/virtio.h b/lib/libvirtio/virtio.h
> index e41f47d..c26282f 100644
> --- a/lib/libvirtio/virtio.h
> +++ b/lib/libvirtio/virtio.h
> @@ -14,6 +14,7 @@
>  #define _LIBVIRTIO_H
>  
>  #include <stdint.h>
> +#include <stdbool.h>
>  
>  /* Device status bits */
>  #define VIRTIO_STAT_ACKNOWLEDGE		1
> @@ -83,6 +84,9 @@ extern int virtio_get_qsize(struct virtio_device *dev, int queue);
>  extern struct vring_desc *virtio_get_vring_desc(struct virtio_device *dev, int queue);
>  extern struct vring_avail *virtio_get_vring_avail(struct virtio_device *dev, int queue);
>  extern struct vring_used *virtio_get_vring_used(struct virtio_device *dev, int queue);
> +extern void virtio_fill_desc(struct vring_desc *desc, bool is_modern,
> +                             uint64_t addr, uint32_t len,
> +                             uint16_t flags, uint16_t next);
>  extern int virtio_queue_init_vq(struct virtio_device *dev, struct vqs *vq, unsigned int id);
>  
>  extern void virtio_reset_device(struct virtio_device *dev);

Anyway, patch also looks ok already as it is, so:

Reviewed-by: Thomas Huth <thuth at redhat.com>