x86, pat: Add lookup_memtype to get the current memtype of a paddr

Add a new routine lookup_memtype() to get the current memtype based on
the PAT reserves and frees.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 45 insertions, 0 deletions

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 1a9d0f07593f..71aa6f7246c6 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -574,6 +574,51 @@ unlock_ret:
 
 
 /**
+ * lookup_memtype - Looksup the memory type for a physical address
+ * @paddr: physical address of which memory type needs to be looked up
+ *
+ * Only to be called when PAT is enabled
+ *
+ * Returns _PAGE_CACHE_WB, _PAGE_CACHE_WC, _PAGE_CACHE_UC_MINUS or
+ * _PAGE_CACHE_UC
+ */
+static unsigned long lookup_memtype(u64 paddr)
+{
+        int rettype = _PAGE_CACHE_WB;
+        struct memtype *entry;
+
+        if (is_ISA_range(paddr, paddr + PAGE_SIZE - 1))
+                return rettype;
+
+        if (pat_pagerange_is_ram(paddr, paddr + PAGE_SIZE)) {
+                struct page *page;
+                spin_lock(&memtype_lock);
+                page = pfn_to_page(paddr >> PAGE_SHIFT);
+                rettype = get_page_memtype(page);
+                spin_unlock(&memtype_lock);
+                /*
+                 * -1 from get_page_memtype() implies RAM page is in its
+                 * default state and not reserved, and hence of type WB
+                 */
+                if (rettype == -1)
+                        rettype = _PAGE_CACHE_WB;
+
+                return rettype;
+        }
+
+        spin_lock(&memtype_lock);
+
+        entry = memtype_rb_search(&memtype_rbroot, paddr);
+        if (entry != NULL)
+                rettype = entry->type;
+        else
+                rettype = _PAGE_CACHE_UC_MINUS;
+
+        spin_unlock(&memtype_lock);
+        return rettype;
+}
+
+/**
  * 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