1 files changed, 106 insertions, 22 deletions

diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c
index 7d28d7d03885..9f27228ceffd 100644
--- a/arch/x86/kernel/cpu/mtrr/generic.c
+++ b/arch/x86/kernel/cpu/mtrr/generic.c
@@ -64,18 +64,59 @@ static inline void k8_check_syscfg_dram_mod_en(void)
         }
 }
 
+/* Get the size of contiguous MTRR range */
+static u64 get_mtrr_size(u64 mask)
+{
+        u64 size;
+
+        mask >>= PAGE_SHIFT;
+        mask |= size_or_mask;
+        size = -mask;
+        size <<= PAGE_SHIFT;
+        return size;
+}
+
 /*
- * Returns the effective MTRR type for the region
- * Error returns:
- * - 0xFE - when the range is "not entirely covered" by _any_ var range MTRR
- * - 0xFF - when MTRR is not enabled
+ * Check and return the effective type for MTRR-MTRR type overlap.
+ * Returns 1 if the effective type is UNCACHEABLE, else returns 0
  */
-u8 mtrr_type_lookup(u64 start, u64 end)
+static int check_type_overlap(u8 *prev, u8 *curr)
+{
+        if (*prev == MTRR_TYPE_UNCACHABLE || *curr == MTRR_TYPE_UNCACHABLE) {
+                *prev = MTRR_TYPE_UNCACHABLE;
+                *curr = MTRR_TYPE_UNCACHABLE;
+                return 1;
+        }
+
+        if ((*prev == MTRR_TYPE_WRBACK && *curr == MTRR_TYPE_WRTHROUGH) ||
+            (*prev == MTRR_TYPE_WRTHROUGH && *curr == MTRR_TYPE_WRBACK)) {
+                *prev = MTRR_TYPE_WRTHROUGH;
+                *curr = MTRR_TYPE_WRTHROUGH;
+        }
+
+        if (*prev != *curr) {
+                *prev = MTRR_TYPE_UNCACHABLE;
+                *curr = MTRR_TYPE_UNCACHABLE;
+                return 1;
+        }
+
+        return 0;
+}
+
+/*
+ * Error/Semi-error returns:
+ * 0xFF - when MTRR is not enabled
+ * *repeat == 1 implies [start:end] spanned across MTRR range and type returned
+ *              corresponds only to [start:*partial_end].
+ *              Caller has to lookup again for [*partial_end:end].
+ */
+static u8 __mtrr_type_lookup(u64 start, u64 end, u64 *partial_end, int *repeat)
 {
         int i;
         u64 base, mask;
         u8 prev_match, curr_match;
 
+        *repeat = 0;
         if (!mtrr_state_set)
                 return 0xFF;
 
@@ -126,8 +167,34 @@ u8 mtrr_type_lookup(u64 start, u64 end)
 
                 start_state = ((start & mask) == (base & mask));
                 end_state = ((end & mask) == (base & mask));
-                if (start_state != end_state)
-                        return 0xFE;
+
+                if (start_state != end_state) {
+                        /*
+                         * We have start:end spanning across an MTRR.
+                         * We split the region into
+                         * either
+                         * (start:mtrr_end) (mtrr_end:end)
+                         * or
+                         * (start:mtrr_start) (mtrr_start:end)
+                         * depending on kind of overlap.
+                         * Return the type for first region and a pointer to
+                         * the start of second region so that caller will
+                         * lookup again on the second region.
+                         * Note: This way we handle multiple overlaps as well.
+                         */
+                        if (start_state)
+                                *partial_end = base + get_mtrr_size(mask);
+                        else
+                                *partial_end = base;
+
+                        if (unlikely(*partial_end <= start)) {
+                                WARN_ON(1);
+                                *partial_end = start + PAGE_SIZE;
+                        }
+
+                        end = *partial_end - 1; /* end is inclusive */
+                        *repeat = 1;
+                }
 
                 if ((start & mask) != (base & mask))
                         continue;
@@ -138,21 +205,8 @@ u8 mtrr_type_lookup(u64 start, u64 end)
                         continue;
                 }
 
-                if (prev_match == MTRR_TYPE_UNCACHABLE ||
-                    curr_match == MTRR_TYPE_UNCACHABLE) {
-                        return MTRR_TYPE_UNCACHABLE;
-                }
-
-                if ((prev_match == MTRR_TYPE_WRBACK &&
-                     curr_match == MTRR_TYPE_WRTHROUGH) ||
-                    (prev_match == MTRR_TYPE_WRTHROUGH &&
-                     curr_match == MTRR_TYPE_WRBACK)) {
-                        prev_match = MTRR_TYPE_WRTHROUGH;
-                        curr_match = MTRR_TYPE_WRTHROUGH;
-                }
-
-                if (prev_match != curr_match)
-                        return MTRR_TYPE_UNCACHABLE;
+                if (check_type_overlap(&prev_match, &curr_match))
+                        return curr_match;
         }
 
         if (mtrr_tom2) {
@@ -166,6 +220,36 @@ u8 mtrr_type_lookup(u64 start, u64 end)
         return mtrr_state.def_type;
 }
 
+/*
+ * Returns the effective MTRR type for the region
+ * Error return:
+ * 0xFF - when MTRR is not enabled
+ */
+u8 mtrr_type_lookup(u64 start, u64 end)
+{
+        u8 type, prev_type;
+        int repeat;
+        u64 partial_end;
+
+        type = __mtrr_type_lookup(start, end, &partial_end, &repeat);
+
+        /*
+         * Common path is with repeat = 0.
+         * However, we can have cases where [start:end] spans across some
+         * MTRR range. Do repeated lookups for that case here.
+         */
+        while (repeat) {
+                prev_type = type;
+                start = partial_end;
+                type = __mtrr_type_lookup(start, end, &partial_end, &repeat);
+
+                if (check_type_overlap(&prev_type, &type))
+                        return type;
+        }
+
+        return type;
+}
+
 /* Get the MSR pair relating to a var range */
 static void
 get_mtrr_var_range(unsigned int index, struct mtrr_var_range *vr)