x86, pat: Use page flags to track memtypes of RAM pages

Change reserve_ram_pages_type and free_ram_pages_type to use 2 page
flags to track UC_MINUS, WC, WB and default types. Previous RAM tracking
just tracked WB or NonWB, which was not complete and did not allow
tracking of RAM fully and there was no way to get the actual type
reserved by looking at the page flags.

We use the memtype_lock spinlock for atomicity in dealing with
memtype tracking in struct page.

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, 52 insertions, 2 deletions

diff --git a/arch/x86/include/asm/cacheflush.h b/arch/x86/include/asm/cacheflush.h
index e55dfc1ad453..b54f6afe7ec4 100644
--- a/arch/x86/include/asm/cacheflush.h
+++ b/arch/x86/include/asm/cacheflush.h
@@ -43,8 +43,58 @@ static inline void copy_from_user_page(struct vm_area_struct *vma,
         memcpy(dst, src, len);
 }
 
-#define PG_non_WB                               PG_arch_1
-PAGEFLAG(NonWB, non_WB)
+#define PG_WC                           PG_arch_1
+PAGEFLAG(WC, WC)
+
+#ifdef CONFIG_X86_PAT
+/*
+ * X86 PAT uses page flags WC and Uncached together to keep track of
+ * memory type of pages that have backing page struct. X86 PAT supports 3
+ * different memory types, _PAGE_CACHE_WB, _PAGE_CACHE_WC and
+ * _PAGE_CACHE_UC_MINUS and fourth state where page's memory type has not
+ * been changed from its default (value of -1 used to denote this).
+ * Note we do not support _PAGE_CACHE_UC here.
+ *
+ * Caller must hold memtype_lock for atomicity.
+ */
+static inline unsigned long get_page_memtype(struct page *pg)
+{
+        if (!PageUncached(pg) && !PageWC(pg))
+                return -1;
+        else if (!PageUncached(pg) && PageWC(pg))
+                return _PAGE_CACHE_WC;
+        else if (PageUncached(pg) && !PageWC(pg))
+                return _PAGE_CACHE_UC_MINUS;
+        else
+                return _PAGE_CACHE_WB;
+}
+
+static inline void set_page_memtype(struct page *pg, unsigned long memtype)
+{
+        switch (memtype) {
+        case _PAGE_CACHE_WC:
+                ClearPageUncached(pg);
+                SetPageWC(pg);
+                break;
+        case _PAGE_CACHE_UC_MINUS:
+                SetPageUncached(pg);
+                ClearPageWC(pg);
+                break;
+        case _PAGE_CACHE_WB:
+                SetPageUncached(pg);
+                SetPageWC(pg);
+                break;
+        default:
+        case -1:
+                ClearPageUncached(pg);
+                ClearPageWC(pg);
+                break;
+        }
+}
+#else
+static inline unsigned long get_page_memtype(struct page *pg) { return -1; }
+static inline void set_page_memtype(struct page *pg, unsigned long memtype) { }
+#endif
 
 /*
  * The set_memory_* API can be used to change various attributes of a virtual