x86: mtrr cleanup for converting continuous to discrete layout, v8

some BIOS like to use continus MTRR layout, and X driver can not add
WB entries for graphical cards when 4g or more RAM installed.

the patch will change MTRR to discrete.

mtrr_chunk_size= could be used to have smaller continuous block to hold holes.
default is 256m, could be set according to size of graphics card memory.

mtrr_gran_size= could be used to send smallest mtrr block to avoid run out of MTRRs

v2: fix -1 for UC checking
v3: default to disable, and need use enable_mtrr_cleanup to enable this feature
    skip the var state change warning.
    remove next_basek in range_to_mtrr()
v4: correct warning mask.
v5: CONFIG_MTRR_SANITIZER
v6: fix 1g, 2g, 512 aligment with extra hole
v7: gran_sizek to prevent running out of MTRRs.
v8: fix hole_basek caculation caused when removing next_basek
    gran_sizek using when basek is 0.

need to apply
	[PATCH] x86: fix trimming e820 with MTRR holes.
right after this one.

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Documentation/kernel-parameters.txt

@@ -599,6 +599,20 @@ and is between 256 and 4096 characters. It is defined in the file
 			See drivers/char/README.epca and
 			Documentation/digiepca.txt.
 
+	disable_mtrr_cleanup [X86]
+	enable_mtrr_cleanup [X86]
+			The kernel tries to adjust MTRR layout from continuous
+			to discrete, to make X server driver able to add WB
+			entry later. This parameter enables/disables that.
+
+	mtrr_chunk_size=nn[KMG] [X86]
+			used for mtrr cleanup. It is largest continous chunk
+			that could hold holes aka. UC entries.
+
+	mtrr_gran_size=nn[KMG] [X86]
+			used for mtrr cleanup. It is granity of mtrr block.
+			Big value could prevent small alignment use up MTRRs.
+
 	disable_mtrr_trim [X86, Intel and AMD only]
 			By default the kernel will trim any uncacheable
 			memory out of your available memory pool based on

arch/x86/Kconfig

@@ -1092,6 +1092,32 @@ config MTRR
 
 	  See <file:Documentation/mtrr.txt> for more information.
 
+config MTRR_SANITIZER
+	def_bool y
+	prompt "MTRR cleanup support"
+	depends on MTRR
+	help
+	  Convert MTRR layout from continuous to discrete, so some X driver
+	  could add WB entries.
+
+	  Say N here if you see bootup problems (boot crash, boot hang,
+	  spontaneous reboots).
+
+	  Could be disabled with disable_mtrr_cleanup. Also mtrr_chunk_size
+	  could be used to send largest mtrr entry size for continuous block
+	  to hold holes (aka. UC entries)
+
+	  If unsure, say Y.
+
+config MTRR_SANITIZER_ENABLE_DEFAULT
+	def_bool y
+	prompt "Enable MTRR cleanup by default"
+	depends on MTRR_SANITIZER
+	help
+	  Enable mtrr cleanup by default
+
+	  If unsure, say Y.
+
 config X86_PAT
 	bool
 	prompt "x86 PAT support"

arch/x86/kernel/cpu/mtrr/generic.c

@@ -37,7 +37,7 @@ 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;
-static u64 tom2;
+u64 mtrr_tom2;
 
 #undef MODULE_PARAM_PREFIX
 #define MODULE_PARAM_PREFIX "mtrr."
@@ -139,8 +139,8 @@ u8 mtrr_type_lookup(u64 start, u64 end)
 		}
 	}
 
-	if (tom2) {
-		if (start >= (1ULL<<32) && (end < tom2))
+	if (mtrr_tom2) {
+		if (start >= (1ULL<<32) && (end < mtrr_tom2))
 			return MTRR_TYPE_WRBACK;
 	}
 
@@ -158,6 +158,20 @@ get_mtrr_var_range(unsigned int index, struct mtrr_var_range *vr)
 	rdmsr(MTRRphysMask_MSR(index), vr->mask_lo, vr->mask_hi);
 }
 
+/*  fill the MSR pair relating to a var range  */
+void fill_mtrr_var_range(unsigned int index,
+		u32 base_lo, u32 base_hi, u32 mask_lo, u32 mask_hi)
+{
+	struct mtrr_var_range *vr;
+
+	vr = mtrr_state.var_ranges;
+
+	vr[index].base_lo = base_lo;
+	vr[index].base_hi = base_hi;
+	vr[index].mask_lo = mask_lo;
+	vr[index].mask_hi = mask_hi;
+}
+
 static void
 get_fixed_ranges(mtrr_type * frs)
 {
@@ -216,10 +230,10 @@ void __init get_mtrr_state(void)
 		unsigned low, high;
 		/* TOP_MEM2 */
 		rdmsr(MSR_K8_TOP_MEM2, low, high);
-		tom2 = high;
-		tom2 <<= 32;
-		tom2 |= low;
-		tom2 &= 0xffffff8000000ULL;
+		mtrr_tom2 = high;
+		mtrr_tom2 <<= 32;
+		mtrr_tom2 |= low;
+		mtrr_tom2 &= 0xffffff8000000ULL;
 	}
 	if (mtrr_show) {
 		int high_width;
@@ -251,9 +265,9 @@ void __init get_mtrr_state(void)
 			else
 				printk(KERN_INFO "MTRR %u disabled\n", i);
 		}
-		if (tom2) {
+		if (mtrr_tom2) {
 			printk(KERN_INFO "TOM2: %016llx aka %lldM\n",
-					  tom2, tom2>>20);
+					  mtrr_tom2, mtrr_tom2>>20);
 		}
 	}
 	mtrr_state_set = 1;