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Re: [Qemu-devel] [PATCH] xen: use native disk xenbus protocol if possibl
From: |
Anthony PERARD |
Subject: |
Re: [Qemu-devel] [PATCH] xen: use native disk xenbus protocol if possible |
Date: |
Wed, 29 Jun 2016 16:20:00 +0100 |
User-agent: |
Mutt/1.6.1 (2016-04-27) |
On Fri, Jun 17, 2016 at 01:14:56PM +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>
> ---
> hw/block/xen_disk.c | 16 ++++++++--------
> 1 file changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/hw/block/xen_disk.c b/hw/block/xen_disk.c
> index 2862b59..0961fcb 100644
> --- a/hw/block/xen_disk.c
> +++ b/hw/block/xen_disk.c
> @@ -976,14 +976,14 @@ 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;
There is one difference with the previous code, in case the protocol is
specified, but it not x86_32 or x86_64, then no blkdev->protocol is
selected (then no ring is initialized). Could you re-add this case?
--
Anthony PERARD