x86: mtrr: add hole punching support

Some ranges would use less variable MTRRs if an UC area
can be carved off the top of larger WB range. Implement this
approach by doing 3 passes over each region in the addres space:
  1. UC default type. Cover non-UC and non-WB regions with respectie type.
     Punch UC hole at upper end of larger WB regions with WB type.
  2. UC default type. Cover non-UC regions with respective type.
  3. WB default type. Cover non-WB regions with respective type.
The hole at upper end of a region uses the same min alignment of 64MiB.

Below are results using a combination of options. The board this was
tested on has 10 variable MTRRs at its disposal. It has 4GiB of RAM.

IO hole config #1: hole starts at 0xad800000

No CACHE_ROM or WRCOMB resources (takes 4 MTRRs):
MTRR: Physical address space:
0x0000000000000000 - 0x00000000000a0000 size 0x000a0000 type 6
0x00000000000a0000 - 0x00000000000c0000 size 0x00020000 type 0
0x00000000000c0000 - 0x00000000ad800000 size 0xad740000 type 6
0x00000000ad800000 - 0x0000000100000000 size 0x52800000 type 0
0x0000000100000000 - 0x000000014f600000 size 0x4f600000 type 6
MTRR: default type WB/UC MTRR counts: 4/9.
MTRR: WB selected as default type.
MTRR: 0 base 0x00000000ad800000 mask 0x0000007fff800000 type 0
MTRR: 1 base 0x00000000ae000000 mask 0x0000007ffe000000 type 0
MTRR: 2 base 0x00000000b0000000 mask 0x0000007ff0000000 type 0
MTRR: 3 base 0x00000000c0000000 mask 0x0000007fc0000000 type 0

No CACHE_ROM. 1 WRCOMB resource (takes 6 MTRRs):
MTRR: Physical address space:
0x0000000000000000 - 0x00000000000a0000 size 0x000a0000 type 6
0x00000000000a0000 - 0x00000000000c0000 size 0x00020000 type 0
0x00000000000c0000 - 0x00000000ad800000 size 0xad740000 type 6
0x00000000ad800000 - 0x00000000d0000000 size 0x22800000 type 0
0x00000000d0000000 - 0x00000000e0000000 size 0x10000000 type 1
0x00000000e0000000 - 0x0000000100000000 size 0x20000000 type 0
0x0000000100000000 - 0x000000014f600000 size 0x4f600000 type 6
MTRR: default type WB/UC MTRR counts: 6/10.
MTRR: WB selected as default type.
MTRR: 0 base 0x00000000ad800000 mask 0x0000007fff800000 type 0
MTRR: 1 base 0x00000000ae000000 mask 0x0000007ffe000000 type 0
MTRR: 2 base 0x00000000b0000000 mask 0x0000007ff0000000 type 0
MTRR: 3 base 0x00000000c0000000 mask 0x0000007ff0000000 type 0
MTRR: 4 base 0x00000000d0000000 mask 0x0000007ff0000000 type 1
MTRR: 5 base 0x00000000e0000000 mask 0x0000007fe0000000 type 0

CACHE_ROM and no WRCOMB resources (taks 10 MTRRs):
MTRR: Physical address space:
0x0000000000000000 - 0x00000000000a0000 size 0x000a0000 type 6
0x00000000000a0000 - 0x00000000000c0000 size 0x00020000 type 0
0x00000000000c0000 - 0x00000000ad800000 size 0xad740000 type 6
0x00000000ad800000 - 0x00000000ff800000 size 0x52000000 type 0
0x00000000ff800000 - 0x0000000100000000 size 0x00800000 type 5
0x0000000100000000 - 0x000000014f600000 size 0x4f600000 type 6
MTRR: default type WB/UC MTRR counts: 11/10.
MTRR: UC selected as default type.
MTRR: 0 base 0x0000000000000000 mask 0x0000007f80000000 type 6
MTRR: 1 base 0x0000000080000000 mask 0x0000007fe0000000 type 6
MTRR: 2 base 0x00000000a0000000 mask 0x0000007ff0000000 type 6
MTRR: 3 base 0x00000000ad800000 mask 0x0000007fff800000 type 0
MTRR: 4 base 0x00000000ae000000 mask 0x0000007ffe000000 type 0
MTRR: 5 base 0x00000000ff800000 mask 0x0000007fff800000 type 0
MTRR: 6 base 0x0000000100000000 mask 0x0000007fc0000000 type 6
MTRR: 7 base 0x0000000140000000 mask 0x0000007ff0000000 type 6
Taking a reserved OS MTRR.
MTRR: 8 base 0x000000014f600000 mask 0x0000007fffe00000 type 0
Taking a reserved OS MTRR.
MTRR: 9 base 0x000000014f800000 mask 0x0000007fff800000 type 0

A combination of CACHE_ROM and WRCOMB just won't work.

IO hole config #2: hole starts at 0x80000000:

No CACHE_ROM or WRCOMB resources (takes 1 MTRR):
MTRR: Physical address space:
0x0000000000000000 - 0x00000000000a0000 size 0x000a0000 type 6
0x00000000000a0000 - 0x00000000000c0000 size 0x00020000 type 0
0x00000000000c0000 - 0x0000000080000000 size 0x7ff40000 type 6
0x0000000080000000 - 0x0000000100000000 size 0x80000000 type 0
0x0000000100000000 - 0x000000017ce00000 size 0x7ce00000 type 6
MTRR: default type WB/UC MTRR counts: 1/5.
MTRR: WB selected as default type.
MTRR: 0 base 0x0000000080000000 mask 0x0000007f80000000 type 0

No CACHE_ROM. 1 WRCOMB resource (takes 4 MTRRs):
MTRR: Physical address space:
0x0000000000000000 - 0x00000000000a0000 size 0x000a0000 type 6
0x00000000000a0000 - 0x00000000000c0000 size 0x00020000 type 0
0x00000000000c0000 - 0x0000000080000000 size 0x7ff40000 type 6
0x0000000080000000 - 0x00000000d0000000 size 0x50000000 type 0
0x00000000d0000000 - 0x00000000e0000000 size 0x10000000 type 1
0x00000000e0000000 - 0x0000000100000000 size 0x20000000 type 0
0x0000000100000000 - 0x000000017ce00000 size 0x7ce00000 type 6
MTRR: default type WB/UC MTRR counts: 4/6.
MTRR: WB selected as default type.
MTRR: 0 base 0x0000000080000000 mask 0x0000007fc0000000 type 0
MTRR: 1 base 0x00000000c0000000 mask 0x0000007ff0000000 type 0
MTRR: 2 base 0x00000000d0000000 mask 0x0000007ff0000000 type 1
MTRR: 3 base 0x00000000e0000000 mask 0x0000007fe0000000 type 0

CACHE_ROM and no WRCOMB resources (takes 6 MTRRs):
MTRR: Physical address space:
0x0000000000000000 - 0x00000000000a0000 size 0x000a0000 type 6
0x00000000000a0000 - 0x00000000000c0000 size 0x00020000 type 0
0x00000000000c0000 - 0x0000000080000000 size 0x7ff40000 type 6
0x0000000080000000 - 0x00000000ff800000 size 0x7f800000 type 0
0x00000000ff800000 - 0x0000000100000000 size 0x00800000 type 5
0x0000000100000000 - 0x000000017ce00000 size 0x7ce00000 type 6
MTRR: default type WB/UC MTRR counts: 9/6.
MTRR: UC selected as default type.
MTRR: 0 base 0x0000000000000000 mask 0x0000007f80000000 type 6
MTRR: 1 base 0x00000000ff800000 mask 0x0000007fff800000 type 0
MTRR: 2 base 0x0000000100000000 mask 0x0000007f80000000 type 6
MTRR: 3 base 0x000000017ce00000 mask 0x0000007fffe00000 type 0
MTRR: 4 base 0x000000017d000000 mask 0x0000007fff000000 type 0
MTRR: 5 base 0x000000017e000000 mask 0x0000007ffe000000 type 0

CACHE_ROM and 1 WRCOMB resource (takes 7 MTRRs):
MTRR: Physical address space:
0x0000000000000000 - 0x00000000000a0000 size 0x000a0000 type 6
0x00000000000a0000 - 0x00000000000c0000 size 0x00020000 type 0
0x00000000000c0000 - 0x0000000080000000 size 0x7ff40000 type 6
0x0000000080000000 - 0x00000000d0000000 size 0x50000000 type 0
0x00000000d0000000 - 0x00000000e0000000 size 0x10000000 type 1
0x00000000e0000000 - 0x00000000ff800000 size 0x1f800000 type 0
0x00000000ff800000 - 0x0000000100000000 size 0x00800000 type 5
0x0000000100000000 - 0x000000017ce00000 size 0x7ce00000 type 6
MTRR: default type WB/UC MTRR counts: 10/7.
MTRR: UC selected as default type.
MTRR: 0 base 0x0000000000000000 mask 0x0000007f80000000 type 6
MTRR: 1 base 0x00000000d0000000 mask 0x0000007ff0000000 type 1
MTRR: 2 base 0x00000000ff800000 mask 0x0000007fff800000 type 0
MTRR: 3 base 0x0000000100000000 mask 0x0000007f80000000 type 6
MTRR: 4 base 0x000000017ce00000 mask 0x0000007fffe00000 type 0
MTRR: 5 base 0x000000017d000000 mask 0x0000007fff000000 type 0
MTRR: 6 base 0x000000017e000000 mask 0x0000007ffe000000 type 0

Change-Id: Iceb9b64991accf558caae2e7b0205951e9bcde44
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/2925
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/cpu/x86/mtrr/mtrr.c

@@ -122,6 +122,21 @@ static inline unsigned int fls(unsigned int x)
 #define RANGE_1MB PHYS_TO_RANGE_ADDR(1 << 20)
 #define RANGE_4GB (1 << (ADDR_SHIFT_TO_RANGE_SHIFT(32)))
 
+/*
+ * The default MTRR type selection uses 3 approaches for selecting the
+ * optimal number of variable MTRRs.  For each range do 3 calculations:
+ *   1. UC as default type with no holes at top of range.
+ *   2. UC as default using holes at top of range.
+ *   3. WB as default.
+ * If using holes is optimal for a range when UC is the default type the
+ * tag is updated to direct the commit routine to use a hole at the top
+ * of a range.
+ */
+#define MTRR_ALGO_SHIFT (8)
+#define MTRR_TAG_MASK ((1 << MTRR_ALGO_SHIFT) - 1)
+/* If the default type is UC use the hole carving algorithm for a range. */
+#define MTRR_RANGE_UC_USE_HOLE (1 << MTRR_ALGO_SHIFT)
+
 static inline uint32_t range_entry_base_mtrr_addr(struct range_entry *r)
 {
 	return PHYS_TO_RANGE_ADDR(range_entry_base(r));
@@ -132,6 +147,11 @@ static inline uint32_t range_entry_end_mtrr_addr(struct range_entry *r)
 	return PHYS_TO_RANGE_ADDR(range_entry_end(r));
 }
 
+static inline int range_entry_mtrr_type(struct range_entry *r)
+{
+	return range_entry_tag(r) & MTRR_TAG_MASK;
+}
+
 static struct memranges *get_physical_address_space(void)
 {
 	static struct memranges *addr_space;
@@ -491,9 +511,72 @@ static void calc_var_mtrr_range(struct var_mtrr_state *var_state,
 	}
 }
 
-static void setup_var_mtrrs_by_state(struct var_mtrr_state *var_state)
+static void calc_var_mtrrs_with_hole(struct var_mtrr_state *var_state,
+                                     struct range_entry *r)
 {
-	struct range_entry *r;
+	uint32_t a1, a2, b1, b2;
+	int mtrr_type;
+	struct range_entry *next;
+
+	/*
+	 * Determine MTRRs based on the following algoirthm for the given entry:
+	 * +------------------+ b2 = ALIGN_UP(end)
+	 * |  0 or more bytes | <-- hole is carved out between b1 and b2
+	 * +------------------+ a2 = b1 = end
+	 * |                  |
+	 * +------------------+ a1 = begin
+	 *
+	 * Thus, there are 3 sub-ranges to configure variable MTRRs for.
+	 */
+	mtrr_type = range_entry_mtrr_type(r);
+
+	a1 = range_entry_base_mtrr_addr(r);
+	a2 = range_entry_end_mtrr_addr(r);
+
+	/* The end address is under 1MiB. The fixed MTRRs take
+	 * precedence over the variable ones. Therefore this range
+	 * can be ignored. */
+	if (a2 < RANGE_1MB)
+		return;
+
+	/* Again, the fixed MTRRs take precedence so the beginning
+	 * of the range can be set to 0 if it starts below 1MiB. */
+	if (a1 < RANGE_1MB)
+		a1 = 0;
+
+	/* If the range starts above 4GiB the processing is done. */
+	if (!var_state->above4gb && a1 >= RANGE_4GB)
+		return;
+
+	/* Clip the upper address to 4GiB if addresses above 4GiB
+	 * are not being processed. */
+	if (!var_state->above4gb && a2 > RANGE_4GB)
+		a2 = RANGE_4GB;
+
+	b1 = a2;
+	b2 = ALIGN_UP(a2, MTRR_MIN_ALIGN);
+
+	/* Check against the next range. If the current range_entry is the
+	 * last entry then carving a hole is no problem. If the current entry
+	 * isn't the last entry then check that the last entry covers the
+	 * entire hole range with the default mtrr type. */
+	next = memranges_next_entry(var_state->addr_space, r);
+	if (next != NULL &&
+	    (range_entry_mtrr_type(next) != var_state->def_mtrr_type ||
+	     range_entry_end_mtrr_addr(next) < b2)) {
+		calc_var_mtrr_range(var_state, a1, a2 - a1, mtrr_type);
+		return;
+	}
+
+	calc_var_mtrr_range(var_state, a1, b2 - a1, mtrr_type);
+	calc_var_mtrr_range(var_state, b1, b2 - b1, var_state->def_mtrr_type);
+}
+
+static void calc_var_mtrrs_without_hole(struct var_mtrr_state *var_state,
+                                         struct range_entry *r)
+{
+	uint32_t a1, a2, b1, b2, c1, c2;
+	int mtrr_type;
 
 	/*
 	 * For each range that meets the non-default type process it in the
@@ -508,13 +591,7 @@ static void setup_var_mtrrs_by_state(struct var_mtrr_state *var_state)
 	 *
 	 * Thus, there are 3 sub-ranges to configure variable MTRRs for.
 	 */
-	memranges_each_entry(r, var_state->addr_space) {
+	mtrr_type = range_entry_mtrr_type(r);
-		uint32_t a1, a2, b1, b2, c1, c2;
-		int mtrr_type = range_entry_tag(r);
-
-		/* Skip default type. */
-		if (var_state->def_mtrr_type == mtrr_type)
-			continue;
 
 	a1 = range_entry_base_mtrr_addr(r);
 	c2 = range_entry_end_mtrr_addr(r);
@@ -523,7 +600,7 @@ static void setup_var_mtrrs_by_state(struct var_mtrr_state *var_state)
 	 * precedence over the variable ones. Therefore this range
 	 * can be ignored. */
 	if (c2 < RANGE_1MB)
-			continue;
+		return;
 
 	/* Again, the fixed MTRRs take precedence so the beginning
 	 * of the range can be set to 0 if it starts below 1MiB. */
@@ -532,7 +609,7 @@ static void setup_var_mtrrs_by_state(struct var_mtrr_state *var_state)
 
 	/* If the range starts above 4GiB the processing is done. */
 	if (!var_state->above4gb && a1 >= RANGE_4GB)
-			break;
+		return;
 
 	/* Clip the upper address to 4GiB if addresses above 4GiB
 	 * are not being processed. */
@@ -543,7 +620,7 @@ static void setup_var_mtrrs_by_state(struct var_mtrr_state *var_state)
 	 * than the minimum granularity. */
 	if ((c2 - a1) < MTRR_MIN_ALIGN) {
 		calc_var_mtrr_range(var_state, a1, c2 - a1, mtrr_type);
-			continue;
+		return;
 	}
 
 	b1 = a2 = ALIGN_UP(a1, MTRR_MIN_ALIGN);
@@ -553,13 +630,13 @@ static void setup_var_mtrrs_by_state(struct var_mtrr_state *var_state)
 	calc_var_mtrr_range(var_state, b1, b2 - b1, mtrr_type);
 	calc_var_mtrr_range(var_state, c1, c2 - c1, mtrr_type);
 }
-}
 
 static int calc_var_mtrrs(struct memranges *addr_space,
                           int above4gb, int address_bits)
 {
 	int wb_deftype_count;
 	int uc_deftype_count;
+	struct range_entry *r;
 	struct var_mtrr_state var_state;
 
 	/* The default MTRR cacheability type is determined by calculating
@@ -570,15 +647,67 @@ static int calc_var_mtrrs(struct memranges *addr_space,
 	var_state.address_bits = address_bits;
 	var_state.commit_mtrrs = 0;
 
+	wb_deftype_count = 0;
+	uc_deftype_count = 0;
+
+	/*
+	 * For each range do 3 calculations:
+	 *   1. UC as default type with no holes at top of range.
+	 *   2. UC as default using holes at top of range.
+	 *   3. WB as default.
+	 * The lowest count is then used as default after totalling all
+	 * MTRRs. Note that the optimal algoirthm for UC default is marked in
+	 * the tag of each range regardless of final decision.  UC takes
+	 * precedence in the MTRR archiecture. Therefore, only holes can be
+	 * used when the type of the region is MTRR_TYPE_WRBACK with
+	 * MTRR_TYPE_UNCACHEABLE as the default type.
+	 */
+	memranges_each_entry(r, var_state.addr_space) {
+		int mtrr_type;
+
+		mtrr_type = range_entry_mtrr_type(r);
+
+		if (mtrr_type != MTRR_TYPE_UNCACHEABLE) {
+			int uc_hole_count;
+			int uc_no_hole_count;
+
+			var_state.def_mtrr_type = MTRR_TYPE_UNCACHEABLE;
+			var_state.mtrr_index = 0;
+
+			/* No hole calculation. */
+			calc_var_mtrrs_without_hole(&var_state, r);
+			uc_no_hole_count = var_state.mtrr_index;
+
+			/* Hole calculation only if type is WB. The 64 number
+			 * is a count that is unachievable, thus making it
+			 * a default large number in the case of not doing
+			 * the hole calculation. */
+			uc_hole_count = 64;
+			if (mtrr_type == MTRR_TYPE_WRBACK) {
+				var_state.mtrr_index = 0;
+				calc_var_mtrrs_with_hole(&var_state, r);
+				uc_hole_count = var_state.mtrr_index;
+			}
+
+			/* Mark the entry with the optimal algorithm. */
+			if (uc_no_hole_count < uc_hole_count) {
+				uc_deftype_count += uc_no_hole_count;
+			} else {
+				unsigned long new_tag;
+
+				new_tag = mtrr_type | MTRR_RANGE_UC_USE_HOLE;
+				range_entry_update_tag(r, new_tag);
+				uc_deftype_count += uc_hole_count;
+			}
+		}
+
+		if (mtrr_type != MTRR_TYPE_WRBACK) {
 			var_state.mtrr_index = 0;
 			var_state.def_mtrr_type = MTRR_TYPE_WRBACK;
-	setup_var_mtrrs_by_state(&var_state);
+			calc_var_mtrrs_without_hole(&var_state, r);
-	wb_deftype_count = var_state.mtrr_index;
+			wb_deftype_count += var_state.mtrr_index;
-
+		}
-	var_state.mtrr_index = 0;
+	}
-	var_state.def_mtrr_type = MTRR_TYPE_UNCACHEABLE;
-	setup_var_mtrrs_by_state(&var_state);
-	uc_deftype_count = var_state.mtrr_index;
 
 	printk(BIOS_DEBUG, "MTRR: default type WB/UC MTRR counts: %d/%d.\n",
 	       wb_deftype_count, uc_deftype_count);
@@ -594,6 +723,7 @@ static int calc_var_mtrrs(struct memranges *addr_space,
 static void commit_var_mtrrs(struct memranges *addr_space, int def_type,
                              int above4gb, int address_bits)
 {
+	struct range_entry *r;
 	struct var_mtrr_state var_state;
 	int i;
 
@@ -604,7 +734,17 @@ static void commit_var_mtrrs(struct memranges *addr_space, int def_type,
 	var_state.commit_mtrrs = 1;
 	var_state.mtrr_index = 0;
 	var_state.def_mtrr_type = def_type;
-	setup_var_mtrrs_by_state(&var_state);
+
+	memranges_each_entry(r, var_state.addr_space) {
+		if (range_entry_mtrr_type(r) == def_type)
+			continue;
+
+		if (def_type == MTRR_TYPE_UNCACHEABLE &&
+		    (range_entry_tag(r) & MTRR_RANGE_UC_USE_HOLE))
+			calc_var_mtrrs_with_hole(&var_state, r);
+		else
+			calc_var_mtrrs_without_hole(&var_state, r);
+	}
 
 	/* Clear all remaining variable MTTRs. */
 	for (i = var_state.mtrr_index; i < total_mtrrs; i++)