Re: [Xen-devel] [RFC PATCH V3 12/16] netback: multi-page ring support

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 30.01.12 at 15:45, Wei Liu <wei.liu2@xxxxxxxxxx> wrote:
> -int xenvif_map_frontend_rings(struct xenvif *vif,
> -                           grant_ref_t tx_ring_ref,
> -                           grant_ref_t rx_ring_ref)
> +int xenvif_map_frontend_rings(struct xen_comms *comms,
> +                           int domid,
> +                           unsigned long ring_ref[],
> +                           unsigned int  ring_ref_count)
>  {
> -     void *addr;
> -     struct xen_netif_tx_sring *txs;
> -     struct xen_netif_rx_sring *rxs;
> -
> -     int err = -ENOMEM;
> +     struct gnttab_map_grant_ref op[NETBK_MAX_RING_PAGES];
> +     unsigned int i;
> +     int err = 0;
>  
> -     err = xenbus_map_ring_valloc(xenvif_to_xenbus_device(vif),
> -                                  tx_ring_ref, &addr);

Any reason why you don't just extend this function (in a prerequisite
patch) rather than open coding a common utility function (twice) here,
so that other backends (blkback!) can benefit later as well.

Jan

> -     if (err)
> -             goto err;
> +     comms->ring_area = alloc_vm_area(PAGE_SIZE * ring_ref_count, NULL);
> +     if (comms->ring_area == NULL)
> +             return -ENOMEM;
>  
> -     txs = (struct xen_netif_tx_sring *)addr;
> -     BACK_RING_INIT(&vif->tx, txs, PAGE_SIZE);
> +     for (i = 0; i < ring_ref_count; i++) {
> +             unsigned long addr = (unsigned long)comms->ring_area->addr +
> +                     (i * PAGE_SIZE);
> +             gnttab_set_map_op(&op[i], addr, GNTMAP_host_map,
> +                               ring_ref[i], domid);
> +     }
>  
> -     err = xenbus_map_ring_valloc(xenvif_to_xenbus_device(vif),
> -                                  rx_ring_ref, &addr);
> -     if (err)
> -             goto err;
> +     if (HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref,
> +                                   &op, ring_ref_count))
> +             BUG();
>  
> -     rxs = (struct xen_netif_rx_sring *)addr;
> -     BACK_RING_INIT(&vif->rx, rxs, PAGE_SIZE);
> +     comms->nr_handles = ring_ref_count;
>  
> -     vif->rx_req_cons_peek = 0;
> +     for (i = 0; i < ring_ref_count; i++) {
> +             if (op[i].status != 0) {
> +                     err = op[i].status;
> +                     comms->shmem_handle[i] = INVALID_GRANT_HANDLE;
> +                     continue;
> +             }
> +             comms->shmem_handle[i] = op[i].handle;
> +     }
>  
> -     return 0;
> +     if (err != 0)
> +             xenvif_unmap_frontend_rings(comms);
>  
> -err:
> -     xenvif_unmap_frontend_rings(vif);
>       return err;
>  }
>  



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