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Re: [Qemu-devel] [PATCH] xen: use native disk xenbus protocol if possibl
From: |
Juergen Gross |
Subject: |
Re: [Qemu-devel] [PATCH] xen: use native disk xenbus protocol if possible |
Date: |
Wed, 29 Jun 2016 17:38:07 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.0 |
On 29/06/16 17:20, Anthony PERARD wrote:
> 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?
Aah, of course!
Thanks,
Juergen