On Tue, Nov 24, 2009 at 08:36:32AM -0600, Anthony Liguori wrote: > Michael S. Tsirkin wrote: >> On Tue, Nov 24, 2009 at 08:54:23AM +1030, Rusty Russell wrote: >> >>> On Tue, 24 Nov 2009 02:37:01 am Shirley Ma wrote: >>> >>>>>> + skb = (struct sk_buff *)buf; >>>>>> >>>>> This cast is unnecessary, but a comment would be nice: >>>>> >>>> Without this cast there is a compile warning. >>> Hi Shirley, >>> >>> Looks like buf is a void *, so no cast should be necessary. But I could >>> be reading the patch wrong. >>> >>> >>>>> However, I question whether making it 16 byte is the right thing: the >>>>> ethernet header is 14 bytes long, so don't we want 8 bytes of padding? >>>>> >>>> Because in QEMU it requires 10 bytes header in a separately, so one page >>>> is used to share between virtio_net_hdr header which is 10 bytes head >>>> and rest of data. So I put 6 bytes offset here between two buffers. I >>>> didn't look at the reason why a seperate buf is used for virtio_net_hdr >>>> in QEMU. >>>> >>> It's a qemu bug. It insists the header be an element in the scatterlist by >>> itself. Unfortunately we have to accommodate it. >>> >> >> We do? Let's just fix this? >> > > So does lguest. It does? All I see it doing is writev/readv, and this passes things to tap which handles this correctly. > It's been that way since the beginning. Fixing this > would result in breaking older guests. If you look at my patch, it handles old guests just fine :). > We really need to introduce a feature bit if we want to change this. I am not sure I agree: we can't add feature bits for all bugs, can we? -- MST -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
