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x86: add clflush before monitor for Intel 7400 series

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For Intel 7400 series CPUs, the recommendation is to use a clflush on the
monitored address just before monitor and mwait pair [1].

This clflush makes sure that there are no false wakeups from mwait when the
monitored address was recently written to.

[1] "MONITOR/MWAIT Recommendations for Intel Xeon Processor 7400 series"
    section in specification update document of 7400 series
    http://download.intel.com/design/xeon/specupdt/32033601.pdf

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Pallipadi, Venkatesh
2009-02-06 16:52:05 -08:00
committed by Ingo Molnar
parent 0cd5c3c80a
commit e736ad548d
3 changed files with 10 additions and 0 deletions
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3
arch/x86/kernel/cpu/intel.c
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@ -291,6 +291,9 @@ static void __cpuinit init_intel(struct cpuinfo_x86 *c)
ds_init_intel(c);
}
if (c->x86 == 6 && c->x86_model == 29 && cpu_has_clflush)
set_cpu_cap(c, X86_FEATURE_CLFLUSH_MONITOR);
#ifdef CONFIG_X86_64
if (c->x86 == 15)
c->x86_cache_alignment = c->x86_clflush_size * 2;