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>

1 files changed, 14 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index e07c432c731f..44427607b7c6 100644
--- a/Documentation/kernel-parameters.txt
+++ b/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