On Sun, Jun 20, 2010 at 02:47:19PM +0300, Michael S. Tsirkin wrote: > > Let's do this then. So far the virtio spec avoided making layout > assumptions, leaving guests lay out data as they see fit. > Isn't it possible to keep supporting this with zero copy for hardware > that can issue DMA at arbitrary addresses? I think you're mistaken with respect to what is being proposed. Raising 512 bytes isn't a hard constraint, it is merely an optimisation for Intel NICs because their PS mode can produce a head fragment of up to 512 bytes. If the guest didn't allocate 512 bytes it wouldn't be the end of the world, it'd just mean that we'd either copy whatever is in the head fragment, or we waste 4096-X bytes of memory where X is the number of bytes in the head. Cheers, -- Visit Openswan at http://www.openswan.org/ Email: Herbert Xu ~{PmV>HI~} <herbert@xxxxxxxxxxxxxxxxxxx> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt -- 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
