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

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 29 Jun 2016, Anthony PERARD wrote:
> 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 <jgross@xxxxxxxx>
> 
> Reviewed-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>

Added to my queue


> > ---
> > 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
> 

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