x86: PAT infrastructure patch

Sets up pat_init() infrastructure.

PAT MSR has following setting.
	PAT
	|PCD
	||PWT
	|||
	000 WB		_PAGE_CACHE_WB
	001 WC		_PAGE_CACHE_WC
	010 UC-		_PAGE_CACHE_UC_MINUS
	011 UC		_PAGE_CACHE_UC

We are effectively changing WT from boot time setting to WC.
UC_MINUS is used to provide backward compatibility to existing /dev/mem
users(X).

reserve_memtype and free_memtype are new interfaces for maintaining alias-free
mapping. It is currently implemented in a simple way with a linked list and
not optimized. reserve and free tracks the effective memory type, as a result
of PAT and MTRR setting rather than what is actually requested in PAT.

pat_init piggy backs on mtrr_init as the rules for setting both pat and mtrr
are same.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 120 insertions, 0 deletions

diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c
index 3e18db4cefe..011e07e99cd 100644
--- a/arch/x86/kernel/cpu/mtrr/generic.c
+++ b/arch/x86/kernel/cpu/mtrr/generic.c
@@ -11,6 +11,7 @@
 #include <asm/cpufeature.h>
 #include <asm/processor-flags.h>
 #include <asm/tlbflush.h>
+#include <asm/pat.h>
 #include "mtrr.h"
 
 struct mtrr_state {
@@ -35,6 +36,7 @@ static struct fixed_range_block fixed_range_blocks[] = {
 
 static unsigned long smp_changes_mask;
 static struct mtrr_state mtrr_state = {};
+static int mtrr_state_set;
 
 #undef MODULE_PARAM_PREFIX
 #define MODULE_PARAM_PREFIX "mtrr."
@@ -42,6 +44,106 @@ static struct mtrr_state mtrr_state = {};
 static int mtrr_show;
 module_param_named(show, mtrr_show, bool, 0);
 
+/*
+ * 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 (prev_match != 0xFF)
+		return prev_match;
+
+	return mtrr_state.def_type;
+}
+
 /*  Get the MSR pair relating to a var range  */
 static void
 get_mtrr_var_range(unsigned int index, struct mtrr_var_range *vr)
@@ -79,12 +181,16 @@ static void print_fixed(unsigned base, unsigned step, const mtrr_type*types)
 			base, base + step - 1, mtrr_attrib_to_str(*types));
 }
 
+static void prepare_set(void);
+static void post_set(void);
+
 /*  Grab all of the MTRR state for this CPU into *state  */
 void __init get_mtrr_state(void)
 {
 	unsigned int i;
 	struct mtrr_var_range *vrs;
 	unsigned lo, dummy;
+	unsigned long flags;
 
 	vrs = mtrr_state.var_ranges;
 
@@ -131,6 +237,17 @@ void __init get_mtrr_state(void)
 				printk(KERN_INFO "MTRR %u disabled\n", i);
 		}
 	}
+	mtrr_state_set = 1;
+
+	/* PAT setup for BP. We need to go through sync steps here */
+	local_irq_save(flags);
+	prepare_set();
+
+	pat_init();
+
+	post_set();
+	local_irq_restore(flags);
+
 }
 
 /*  Some BIOS's are fucked and don't set all MTRRs the same!  */
@@ -397,6 +514,9 @@ static void generic_set_all(void)
 	/* Actually set the state */
 	mask = set_mtrr_state();
 
+	/* also set PAT */
+	pat_init();
+
 	post_set();
 	local_irq_restore(flags);