x86: mtrr cleanup for converting continuous to discrete - auto detect v4

Loop through mtrr chunk_size and gran_size from 1M to 2G to find out
the optimal value so user does not need to add mtrr_chunk_size and
mtrr_gran_size to the kernel command line.

If optimal value is not found, print out all list to help select less
optimal value.

Add mtrr_spare_reg_nr= so user could set 2 instead of 1, if the card
need more entries.

v2: find the one with more spare entries
v3: fix hole_basek offset
v4: tight the compare between range and range_new
    loop stop with 4g
Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Gabriel C <nix.or.die@googlemail.com>
Cc: Mika Fischer <mika.fischer@zoopnet.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Documentation/kernel-parameters.txt

@@ -610,8 +610,17 @@ and is between 256 and 4096 characters. It is defined in the file
 			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.
+			Used for mtrr cleanup. It is granularity of mtrr block.
+			Default is 1.
+			Large value could prevent small alignment from
+			using up MTRRs.
+
+	mtrr_spare_reg_nr=n [X86]
+			Format: <integer>
+			Range: 0,7 : spare reg number
+			Default : 1
+			Used for mtrr cleanup. It is spare mtrr entries number.
+			Set to 2 or more if your graphical card needs more.
 
 	disable_mtrr_trim [X86, Intel and AMD only]
 			By default the kernel will trim any uncacheable

arch/x86/Kconfig

@@ -1117,6 +1117,15 @@ config MTRR_SANITIZER_ENABLE_DEFAULT
 	help
 	  Enable mtrr cleanup default value
 
+config MTRR_SANITIZER_SPARE_REG_NR_DEFAULT
+	int "MTRR cleanup spare reg num (0-7)"
+	range 0 7
+	default "1"
+	depends on MTRR_SANITIZER
+	help
+	  mtrr cleanup spare entries default, it can be changed via
+	  mtrr_spare_reg_nr=
+
 config X86_PAT
 	bool
 	prompt "x86 PAT support"