+/*
+ * 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
+ */
+u8 mtrr_type_lookup(u64 start, u64 end)
+{
+ int i;
+ u64 base, mask;
+ u8 prev_match, curr_match;
+
+ if (!mtrr_state_set)
+ return 0xFF;
+
+ if (!mtrr_state.enabled)
+ return 0xFF;
+
+ /* Make end inclusive end, instead of exclusive */
+ end--;
+
+ /* Look in fixed ranges. Just return the type as per start */
+ if (mtrr_state.have_fixed && (start < 0x100000)) {
+ int idx;
+
+ if (start < 0x80000) {
+ idx = 0;
+ idx += (start >> 16);
+ return mtrr_state.fixed_ranges[idx];
+ } else if (start < 0xC0000) {
+ idx = 1 * 8;
+ idx += ((start - 0x80000) >> 14);
+ return mtrr_state.fixed_ranges[idx];
+ } else if (start < 0x1000000) {
+ idx = 3 * 8;
+ idx += ((start - 0xC0000) >> 12);
+ return mtrr_state.fixed_ranges[idx];
+ }
+ }
+
+ /*
+ * Look in variable ranges
+ * Look of multiple ranges matching this address and pick type
+ * as per MTRR precedence
+ */
+ if (!(mtrr_state.enabled & 2)) {
+ return mtrr_state.def_type;
+ }
+
+ prev_match = 0xFF;
+ for (i = 0; i < num_var_ranges; ++i) {
+ unsigned short start_state, end_state;
+
+ if (!(mtrr_state.var_ranges[i].mask_lo & (1 << 11)))
+ continue;
+
+ base = (((u64)mtrr_state.var_ranges[i].base_hi) << 32) +
+ (mtrr_state.var_ranges[i].base_lo & PAGE_MASK);
+ mask = (((u64)mtrr_state.var_ranges[i].mask_hi) << 32) +
+ (mtrr_state.var_ranges[i].mask_lo & PAGE_MASK);
+
+ start_state = ((start & mask) == (base & mask));
+ end_state = ((end & mask) == (base & mask));
+ if (start_state != end_state)
+ return 0xFE;
+
+ if ((start & mask) != (base & mask)) {
+ continue;
+ }
+
+ curr_match = mtrr_state.var_ranges[i].base_lo & 0xff;
+ if (prev_match == 0xFF) {
+ prev_match = curr_match;
+ 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 (mtrr_tom2) {
+ if (start >= (1ULL<<32) && (end < mtrr_tom2))
+ return MTRR_TYPE_WRBACK;
+ }
+
+ if (prev_match != 0xFF)
+ return prev_match;
+
+ return mtrr_state.def_type;
+}
+