Re: [Qemu-devel] [PATCH v2] xen: use native disk xenbus protocol if possible

[Anthony PERARD]

On Wed, Jun 29, 2016 at 05:50:48PM +0200, Juergen Gross wrote:
> The qdisk implementation is using the native xenbus protocol only in
> case of no protocol specified at all. As using the explicit 32- or
> 64-bit protocol is slower than the native one due to copying requests
> not by memcpy but element for element, this is not optimal.
> 
> Correct this by using the native protocol in case word sizes of
> frontend and backend match.
> 
> Signed-off-by: Juergen Gross <address@hidden>

Reviewed-by: Anthony PERARD <address@hidden>

Thanks,

> ---
> V2: use native protocol in case of unknown protocol specified as
>     requested by Anthony Perard
> ---
>  hw/block/xen_disk.c | 18 ++++++++++--------
>  1 file changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/hw/block/xen_disk.c b/hw/block/xen_disk.c
> index 90aca73..d0aae67 100644
> --- a/hw/block/xen_disk.c
> +++ b/hw/block/xen_disk.c
> @@ -975,14 +975,16 @@ static int blk_connect(struct XenDevice *xendev)
>          blkdev->feature_persistent = !!pers;
>      }
>  
> -    blkdev->protocol = BLKIF_PROTOCOL_NATIVE;
> -    if (blkdev->xendev.protocol) {
> -        if (strcmp(blkdev->xendev.protocol, XEN_IO_PROTO_ABI_X86_32) == 0) {
> -            blkdev->protocol = BLKIF_PROTOCOL_X86_32;
> -        }
> -        if (strcmp(blkdev->xendev.protocol, XEN_IO_PROTO_ABI_X86_64) == 0) {
> -            blkdev->protocol = BLKIF_PROTOCOL_X86_64;
> -        }
> +    if (!blkdev->xendev.protocol) {
> +        blkdev->protocol = BLKIF_PROTOCOL_NATIVE;
> +    } else if (strcmp(blkdev->xendev.protocol, XEN_IO_PROTO_ABI_NATIVE) == 
> 0) {
> +        blkdev->protocol = BLKIF_PROTOCOL_NATIVE;
> +    } else if (strcmp(blkdev->xendev.protocol, XEN_IO_PROTO_ABI_X86_32) == 
> 0) {
> +        blkdev->protocol = BLKIF_PROTOCOL_X86_32;
> +    } else if (strcmp(blkdev->xendev.protocol, XEN_IO_PROTO_ABI_X86_64) == 
> 0) {
> +        blkdev->protocol = BLKIF_PROTOCOL_X86_64;
> +    } else {
> +        blkdev->protocol = BLKIF_PROTOCOL_NATIVE;
>      }
>  
>      blkdev->sring = xengnttab_map_grant_ref(blkdev->xendev.gnttabdev,
> -- 
> 2.6.6
> 

-- 
Anthony PERARD