[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH net-next] xen-netback: fix xenvif_count_skb_slots()
> -----Original Message----- > From: Wei Liu [mailto:wei.liu2@xxxxxxxxxx] > Sent: 07 October 2013 11:02 > To: Paul Durrant > Cc: xen-devel@xxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; Xi Xiong; Matt Wilson; > Annie Li; Wei Liu; Ian Campbell > Subject: Re: [PATCH net-next] xen-netback: fix xenvif_count_skb_slots() > > On Fri, Oct 04, 2013 at 05:26:23PM +0100, Paul Durrant wrote: > > Commit 4f0581d25827d5e864bcf07b05d73d0d12a20a5c introduced an error > into > > xenvif_count_skb_slots() for skbs with a linear area spanning a page > > boundary. The alignment of skb->data needs to be taken into account, not > > just the head length. This patch fixes the issue by dry-running the code > > from xenvif_gop_skb() (and adjusting the comment above the function to > note > > that). > > > > If I'm not mistaken the change in commit 4f0581d2 is correct because we > changed the way that the ring is packed. Now you seem to fall back to > the original scheme (or something in between without reverting later > other changes in that commit). > It's not possible to use a single grant copy to copy to even a 2-byte linear area that spans a page boundary so you have to take into account the alignment of skb->data. How the ring is packed is not relevant. > Do you have instruction to reproduce the bug? Can you paste some > detailed oops message? > I don't have the message to hand, but it's this BUG_ON that I hit: BUG_ON(npo.copy_prod > ARRAY_SIZE(vif->grant_copy_op)); I.e. we blow the grant copy op array. Paul _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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