lkml.org 
[lkml]   [2012]   [Apr]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2 03/16] KVM: MMU: properly assert spte on rmap walking path
On Fri, 13 Apr 2012 18:10:45 +0800
Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> 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


\
 
 \ /
  Last update: 2012-04-14 04:17    [W:0.285 / U:0.288 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site