1 files changed, 19 insertions, 0 deletions
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index fe7d57a8fb60..1555bd7d3449 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -678,6 +678,25 @@ static enum page_cache_mode lookup_memtype(u64 paddr)
 }
 
 /**
+ * pat_pfn_immune_to_uc_mtrr - Check whether the PAT memory type
+ * of @pfn cannot be overridden by UC MTRR memory type.
+ *
+ * Only to be called when PAT is enabled.
+ *
+ * Returns true, if the PAT memory type of @pfn is UC, UC-, or WC.
+ * Returns false in other cases.
+ */
+bool pat_pfn_immune_to_uc_mtrr(unsigned long pfn)
+{
+	enum page_cache_mode cm = lookup_memtype(PFN_PHYS(pfn));
+
+	return cm == _PAGE_CACHE_MODE_UC ||
+	       cm == _PAGE_CACHE_MODE_UC_MINUS ||
+	       cm == _PAGE_CACHE_MODE_WC;
+}
+EXPORT_SYMBOL_GPL(pat_pfn_immune_to_uc_mtrr);
+
+/**
  * io_reserve_memtype - Request a memory type mapping for a region of memory
  * @start: start (physical address) of the region
  * @end: end (physical address) of the region