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

On 2013-3-13 4:13, Wei Liu wrote:
Actually the copy is done with Hypervisor, I don't know how it is
possible to do coalesce while copying.

My understanding is we do coalescing in netback during grant copy. For example,

                 gop->source.u.ref = txreq.gref;
                 gop->source.domid = vif->domid;
                 gop->source.offset = txreq.offset;

gop->dest.u.gmfn = virt_to_mfn(page_address(page)); -- here should be the page where we coalesce data into, it is likely the page is the one which previous request used.
                 gop->dest.domid = DOMID_SELF;
gop->dest.offset = txreq.offset; -- dest.offset should be changed to something which represents the offset where we start coalescing data of this request

gop->len = txreq.size; -- len should be the total len of data which we coalesce into a page
                 gop->flags = GNTCOPY_source_gref;

With this coalescing, it is possible that we could decrease the total frags number of skb in netback.


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