Rusty Russell wrote:

Finally, a scatter-gather list mechanism allows the domains to
associate their pages with arbitrary queue numbers in the shared
region, to transport bulk data (effectively by having the hypervisor
do "DMA" between domains).

> +/* Copy from src to dst, return amount copied. */
+static int do_copy(const struct sg_list *sgdst, const struct sg_list *sgsrc,
+ unsigned long (*copy)(paddr_t, paddr_t, unsigned long))
+{
+ unsigned long totlen, src, dst, srcoff, dstoff;
+ int ret = 0;
+
+ totlen = 0;
+ src = dst = 0;
+ srcoff = dstoff = 0;
+ while (src < sgsrc->num_sg) {
+ unsigned long len;
+ len = min(sgsrc->sg[src].len - srcoff,
+ sgdst->sg[dst].len - dstoff);
+
+ len = copy(sgdst->sg[dst].addr+dstoff,
+ sgsrc->sg[src].addr+srcoff,
+ len);

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