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>

1 files changed, 11 insertions, 2 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 44427607b7c6..2000977af776 100644
--- a/Documentation/kernel-parameters.txt
+++ b/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