Re: [Xen-devel] Is: SKB_MAX_LEN bites again. Was: Re: bug disabling guest interface

[ANNIE LI <annie.li@xxxxxxxxxx>]

On 2013-3-9 4:36, Konrad Rzeszutek Wilk wrote:
> On Fri, Mar 08, 2013 at 08:36:37PM +0100, Jacek Milewicz wrote:
> > Hi All
> >
> > > Is there any further information on a possible fix for this? Thoughts?
> > > Ideas? As it seems to be hitting multiple sites, I'd like to get it
> > fixed asap...
> >
> > There are 3 ways I can see this fixed:
> > - update guests so all have same MAX_SKB_FRAGS (that includes windows
> > drivers (windows drivers use 19 for MAX_SKB_FRAGS))
> > -add some sort of negotiation between host and guest
> > - change MAX_SKB_FRAGS to 19 to accommodate all guests
> >
> > Unfortunately first one requires changes to the guest and most don't have
> > that luxury. So the only way I see it could be fixed without breaking
> > compatibility even more  is
> Ugh. The negotiations between host and guest is probably the best
> choice. The issues you are going to hit are that you might need
> to redo the skbs to match what the frontend's max is.
>
> Annie, Wei, Ian - were there some RFC patches floating around
> for this?
Actually I did plan to do it, but failed to start it because of windows 
WHQL things.
Thanks
Annie
> > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> > index 821c7f4..82de0f5 100644
> > --- a/include/linux/skbuff.h
> > +++ b/include/linux/skbuff.h
> > @@ -143,8 +143,8 @@ struct sk_buff;
> >    * Since GRO uses frags we allocate at least 16 regardless of page
> >    * size.
> >    */
> > -#if (65536/PAGE_SIZE + 1)<  16
> > -#define MAX_SKB_FRAGS 16UL
> > +#if (65536/PAGE_SIZE + 1)<  19
> > +#define MAX_SKB_FRAGS 19UL
> >   #else
> >   #define MAX_SKB_FRAGS (65536/PAGE_SIZE + 1)
> >   #endif
> >
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxx
> > http://lists.xen.org/xen-devel
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