diff options
authorSuresh Siddha <suresh.b.siddha@intel.com>2009-09-16 14:28:03 -0700
committerH. Peter Anvin <hpa@zytor.com>2009-09-17 14:07:58 -0700
commitdcb73bf402e0d5b28ce925dbbe4dab3b00b21eee (patch)
parentfa526d0d641b5365676a1fb821ce359e217c9b85 (diff)
x86, pat: don't use rb-tree based lookup in reserve_memtype()
Recent enhancement of rb-tree based lookup exposed a bug with the lookup mechanism in the reserve_memtype() which ensures that there are no conflicting memtype requests for the memory range. memtype_rb_search() returns an entry which has a start address <= new start address. And from here we traverse the linear linked list to check if there any conflicts with the existing mappings. As the rbtree is based on the start address of the memory range, it is quite possible that we have several overlapped mappings whose start address is much less than new requested start but the end is >= new requested end. This results in conflicting memtype mappings. Same bug exists with the old code which uses cached_entry from where we traverse the linear linked list. But the new rb-tree code exposes this bug fairly easily. For now, don't use the memtype_rb_search() and always start the search from the head of linear linked list in reserve_memtype(). Linear linked list for most of the systems grow's to few 10's of entries(as we track memory type of RAM pages using struct page). So we should be ok for now. We still retain the rbtree and use it to speed up free_memtype() which doesn't have the same bug(as we know what exactly we are searching for in free_memtype). Also use list_for_each_entry_from() in free_memtype() so that we start the search from rb-tree lookup result. Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de> Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> LKML-Reference: <1253136483.4119.12.camel@sbs-t61.sc.intel.com> Signed-off-by: H. Peter Anvin <hpa@zytor.com>
1 files changed, 2 insertions, 10 deletions
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index d2a72abc9de1..9b647f679389 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -424,17 +424,9 @@ int reserve_memtype(u64 start, u64 end, unsigned long req_type,
- entry = memtype_rb_search(&memtype_rbroot, new->start);
- if (likely(entry != NULL)) {
- /* To work correctly with list_for_each_entry_continue */
- entry = list_entry(entry->nd.prev, struct memtype, nd);
- } else {
- entry = list_entry(&memtype_list, struct memtype, nd);
- }
/* Search for existing mapping that overlaps the current range */
where = NULL;
- list_for_each_entry_continue(entry, &memtype_list, nd) {
+ list_for_each_entry(entry, &memtype_list, nd) {
if (end <= entry->start) {
where = entry->nd.prev;
@@ -532,7 +524,7 @@ int free_memtype(u64 start, u64 end)
* in sorted start address
saved_entry = entry;
- list_for_each_entry(entry, &memtype_list, nd) {
+ list_for_each_entry_from(entry, &memtype_list, nd) {
if (entry->start == start && entry->end == end) {
rb_erase(&entry->rb, &memtype_rbroot);