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From: Juergen Gross <jgross@suse.com>
To: Anthony PERARD <anthony.perard@citrix.com>
Cc: xen-devel@lists.xensource.com, sstabellini@kernel.org,
	qemu-devel@nongnu.org, kraxel@redhat.com
Subject: Re: [PATCH] xen: use native disk xenbus protocol if possible
Date: Wed, 29 Jun 2016 17:38:07 +0200	[thread overview]
Message-ID: <5773EB5F.4060407@suse.com> (raw)
In-Reply-To: <20160629152000.GA5666@perard.uk.xensource.com>

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 <jgross@suse.com>
>> ---
>>  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

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      reply	other threads:[~2016-06-29 15:38 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-17 11:14 [PATCH] xen: use native disk xenbus protocol if possible Juergen Gross
2016-06-27 10:54 ` [Xen-devel] " Juergen Gross
2016-06-29 15:20 ` Anthony PERARD
2016-06-29 15:38   ` Juergen Gross [this message]

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