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-rw-r--r--arch/x86/mm/pat.c49
1 files changed, 24 insertions, 25 deletions
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index de3a9981245..183fdd36d3b 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -151,32 +151,33 @@ static int pat_x_mtrr_type(u64 start, u64 end, unsigned long prot,
unsigned long pat_type;
u8 mtrr_type;
- mtrr_type = mtrr_type_lookup(start, end);
- if (mtrr_type == 0xFF) { /* MTRR not enabled */
- *ret_prot = prot;
- return 0;
- }
- if (mtrr_type == 0xFE) { /* MTRR match error */
- *ret_prot = _PAGE_CACHE_UC;
- return -1;
- }
- if (mtrr_type != MTRR_TYPE_UNCACHABLE &&
- mtrr_type != MTRR_TYPE_WRBACK &&
- mtrr_type != MTRR_TYPE_WRCOMB) { /* MTRR type unhandled */
- *ret_prot = _PAGE_CACHE_UC;
- return -1;
- }
-
pat_type = prot & _PAGE_CACHE_MASK;
prot &= (~_PAGE_CACHE_MASK);
- /* Currently doing intersection by hand. Optimize it later. */
+ /*
+ * We return the PAT request directly for types where PAT takes
+ * precedence with respect to MTRR and for UC_MINUS.
+ * Consistency checks with other PAT requests is done later
+ * while going through memtype list.
+ */
if (pat_type == _PAGE_CACHE_WC) {
*ret_prot = prot | _PAGE_CACHE_WC;
+ return 0;
} else if (pat_type == _PAGE_CACHE_UC_MINUS) {
*ret_prot = prot | _PAGE_CACHE_UC_MINUS;
- } else if (pat_type == _PAGE_CACHE_UC ||
- mtrr_type == MTRR_TYPE_UNCACHABLE) {
+ return 0;
+ } else if (pat_type == _PAGE_CACHE_UC) {
+ *ret_prot = prot | _PAGE_CACHE_UC;
+ return 0;
+ }
+
+ /*
+ * Look for MTRR hint to get the effective type in case where PAT
+ * request is for WB.
+ */
+ mtrr_type = mtrr_type_lookup(start, end);
+
+ if (mtrr_type == MTRR_TYPE_UNCACHABLE) {
*ret_prot = prot | _PAGE_CACHE_UC;
} else if (mtrr_type == MTRR_TYPE_WRCOMB) {
*ret_prot = prot | _PAGE_CACHE_WC;
@@ -233,14 +234,12 @@ int reserve_memtype(u64 start, u64 end, unsigned long req_type,
if (req_type == -1) {
/*
- * Special case where caller wants to inherit from mtrr or
- * existing pat mapping, defaulting to UC_MINUS in case of
- * no match.
+ * Call mtrr_lookup to get the type hint. This is an
+ * optimization for /dev/mem mmap'ers into WB memory (BIOS
+ * tools and ACPI tools). Use WB request for WB memory and use
+ * UC_MINUS otherwise.
*/
u8 mtrr_type = mtrr_type_lookup(start, end);
- if (mtrr_type == 0xFE) { /* MTRR match error */
- err = -1;
- }
if (mtrr_type == MTRR_TYPE_WRBACK) {
req_type = _PAGE_CACHE_WB;