On Fri, 13 Apr 2012 18:10:45 +0800
Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx> wrote:
> static u64 *rmap_get_next(struct rmap_iterator *iter)
> {
> + u64 *sptep = NULL;
> +
> if (iter->desc) {
> if (iter->pos < PTE_LIST_EXT - 1) {
> - u64 *sptep;
> -
> ++iter->pos;
> sptep = iter->desc->sptes[iter->pos];
> if (sptep)
> - return sptep;
> + goto exit;
> }
>
> iter->desc = iter->desc->more;
> @@ -1028,11 +1036,14 @@ static u64 *rmap_get_next(struct rmap_iterator *iter)
> if (iter->desc) {
> iter->pos = 0;
> /* desc->sptes[0] cannot be NULL */
> - return iter->desc->sptes[iter->pos];
> + sptep = iter->desc->sptes[iter->pos];
> + goto exit;
> }
> }
>
> - return NULL;
> +exit:
> + WARN_ON(sptep && !is_shadow_present_pte(*sptep));
> + return sptep;
> }
This will, probably, again force rmap_get_next function-call even with EPT/NPT:
CPU cannot skip it by branch prediction.
Takuya
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