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>

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 1a9d0f07593f60782f85f9996ae7abff5e5b16dc..71aa6f7246c68214fd14f6394f3fec85c6222c1e 100644 (file)
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -573,6 +573,51 @@ 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