x86/mtrr: Resolve inconsistency with Intel processor manual

Following is from Notes of section 11.5.3 of Intel processor
manual available at:

  http://www.intel.com/Assets/PDF/manual/325384.pdf

For the Pentium 4 and Intel Xeon processors, after the sequence of
steps given above has been executed, the cache lines containing the
code between the end of the WBINVD instruction and before the
MTRRS have actually been disabled may be retained in the cache
hierarchy. Here, to remove code from the cache completely, a
second WBINVD instruction must be executed after the MTRRs have
been disabled.

This patch provides resolution for that.

Ideally, I will like to make changes only for Pentium 4 and Xeon
processors. But, I am not finding easier way to do it.
And, extra wbinvd() instruction does not hurt much for other
processors.

Signed-off-by: Ajaykumar Hotchandani <ajaykumar.hotchandani@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Lucas De Marchi <lucas.demarchi@profusion.mobi>
Link: http://lkml.kernel.org/r/4EBD1CC5.3030008@oracle.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c
index e1fe7f42e0fbd02700df1da8ba5925af48e7264e..97b26356e9ee8b022b45ae1adc5ef7628a5e2539 100644 (file)
--- a/arch/x86/kernel/cpu/mtrr/generic.c
+++ b/arch/x86/kernel/cpu/mtrr/generic.c
@@ -694,6 +694,7 @@ static void prepare_set(void) __acquires(set_atomicity_lock)
 
        /* Disable MTRRs, and set the default type to uncached */
        mtrr_wrmsr(MSR_MTRRdefType, deftype_lo & ~0xcff, deftype_hi);
+       wbinvd();
 }
 
 static void post_set(void) __releases(set_atomicity_lock)