diff options
| author | Pallipadi, Venkatesh <venkatesh.pallipadi@intel.com> | 2009-07-30 14:43:19 -0700 |
|---|---|---|
| committer | H. Peter Anvin <hpa@zytor.com> | 2009-07-30 17:48:34 -0700 |
| commit | bdc6340f4eb68295b1e7c0ade2356b56dca93d93 (patch) | |
| tree | 5ea11ad6a56840ea7c35bafd9c2ca3c6430a3154 | |
| parent | 0e83815be719d3391bf5ea24b7fe696c07dbd417 (diff) | |
x86, pat: Fix set_memory_wc related corruption
Changeset 3869c4aa18835c8c61b44bd0f3ace36e9d3b5bd0
that went in after 2.6.30-rc1 was a seemingly small change to _set_memory_wc()
to make it complaint with SDM requirements. But, introduced a nasty bug, which
can result in crash and/or strange corruptions when set_memory_wc is used.
One such crash reported here
http://lkml.org/lkml/2009/7/30/94
Actually, that changeset introduced two bugs.
* change_page_attr_set() takes &addr as first argument and can the addr value
might have changed on return, even for single page change_page_attr_set()
call. That will make the second change_page_attr_set() in this routine
operate on unrelated addr, that can eventually cause strange corruptions
and bad page state crash.
* The second change_page_attr_set() call, before setting _PAGE_CACHE_WC, should
clear the earlier _PAGE_CACHE_UC_MINUS, as otherwise cache attribute will not
be WC (will be UC instead).
The patch below fixes both these problems. Sending a single patch to fix both
the problems, as the change is to the same line of code. The change to have a
addr_copy is not very clean. But, it is simpler than making more changes
through various routines in pageattr.c.
A huge thanks to Jerome for reporting this problem and providing a simple test
case that helped us root cause the problem.
Reported-by: Jerome Glisse <glisse@freedesktop.org>
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
LKML-Reference: <20090730214319.GA1889@linux-os.sc.intel.com>
Acked-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
| -rw-r--r-- | arch/x86/mm/pageattr.c | 9 |
1 files changed, 6 insertions, 3 deletions
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index 1b734d7a8966..895d90e1a81b 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -997,12 +997,15 @@ EXPORT_SYMBOL(set_memory_array_uc); int _set_memory_wc(unsigned long addr, int numpages) { int ret; + unsigned long addr_copy = addr; + ret = change_page_attr_set(&addr, numpages, __pgprot(_PAGE_CACHE_UC_MINUS), 0); - if (!ret) { - ret = change_page_attr_set(&addr, numpages, - __pgprot(_PAGE_CACHE_WC), 0); + ret = change_page_attr_set_clr(&addr_copy, numpages, + __pgprot(_PAGE_CACHE_WC), + __pgprot(_PAGE_CACHE_MASK), + 0, 0, NULL); } return ret; } |