[coreboot-gerrit] Patch merged into coreboot/master: 7756fe7 x86: Minimize work done with the caches disabled in mtrr functions.

[gerrit at coreboot.org]

the following patch was just integrated into master:
commit 7756fe70eb568e1429e244306be9401357cefa43
Author: Gabe Black <gabeblack at google.com>
Date:   Tue Feb 25 01:40:34 2014 -0800

    x86: Minimize work done with the caches disabled in mtrr functions.
    
    The code in src/cpu/x86/mtrr/mtrr.c disables caching in a few places when
    changing mtrr settings. While I can't find anything that says that's actually
    required, I can believe it's necessary. With that said, other code around the
    wrmsr instructions which actually modify the settings should be able to run
    with caching enabled with no ill effects.
    
    This is particularly true for two calls to printk, one in the fixed mtrr code
    and one in the variable, which could result in an arbitrary amount of work
    being done without caching. When changing the implementation of the cbmem
    console, these two printks caused a significant regression in boot performance
    on link of about 70ms which is about 10% of total firmware boot time. When the
    window where the cache is disabled is minimized, both this and the new
    implementation were about 30ms faster than the original boot time.
    
    For the variable MTRRs, we now store what we want to set the MSRs to and then
    write them all at once at the end of commit_var_mtrrs(). This way we don't
    have some set and some not, but we still minimize the time we spend with the
    caches disabled.
    
    Change-Id: I5139b262bd2d13f79afd88e2e2c0f514fb3e27c9
    Signed-off-by: Gabe Black <gabeblack at google.com>
    Reviewed-on: https://chromium-review.googlesource.com/187811
    Reviewed-by: Ronald Minnich <rminnich at chromium.org>
    Reviewed-by: Aaron Durbin <adurbin at chromium.org>
    Commit-Queue: Gabe Black <gabeblack at chromium.org>
    Tested-by: Gabe Black <gabeblack at chromium.org>
    (cherry picked from commit 31529d6d965676c6cedeb62137eabc26819956fc)
    Signed-off-by: Isaac Christensen <isaac.christensen at se-eng.com>
    Reviewed-on: http://review.coreboot.org/6952
    Tested-by: build bot (Jenkins)
    Reviewed-by: Edward O'Callaghan <eocallaghan at alterapraxis.com>


See http://review.coreboot.org/6952 for details.

-gerrit