aboutsummaryrefslogtreecommitdiff
path: root/arch/x86
diff options
context:
space:
mode:
authorvenkatesh.pallipadi@intel.com <venkatesh.pallipadi@intel.com>2009-04-09 14:26:50 -0700
committerIngo Molnar <mingo@elte.hu>2009-04-10 13:55:47 +0200
commit3869c4aa18835c8c61b44bd0f3ace36e9d3b5bd0 (patch)
treec983ab8206233bd571ff10ce307826a2e4126cc1 /arch/x86
parent9fa3ab390abfc8b49fc0dd7c845b0ad224ec429f (diff)
x86, PAT: Changing memtype to WC ensuring no WB alias
As per SDM, there should not be any aliasing of a WC with any cacheable type across CPUs. That is if one CPU is changing the identity map memtype to _WC, no other CPU at the time of this change should not have a TLB for this page that carries a WB attribute. SDM suggests to make the page not present. But for that we will have to handle any page faults that can potentially happen due to these pages being not present. Other way to deal with this without having any WB mapping is to change the page first to UC and then to WC. This ensures that we meet the SDM requirement of no cacheable alais to WC page. This also has same or lower overhead than marking the page not present and making it present later. Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> LKML-Reference: <20090409212708.797481000@intel.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/mm/pageattr.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 985eef80c55..797f9f107cb 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -1000,8 +1000,15 @@ EXPORT_SYMBOL(set_memory_array_uc);
int _set_memory_wc(unsigned long addr, int numpages)
{
- return change_page_attr_set(&addr, numpages,
+ int ret;
+ 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);
+ }
+ return ret;
}
int set_memory_wc(unsigned long addr, int numpages)