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x86: Implement support to synchronize RDTSC with LFENCE on Intel CPUs

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According to Intel RDTSC can be always synchronized with LFENCE
on all current CPUs. Implement the necessary CPUID bit for that.

It is unclear yet if that is true for all future CPUs too,
but if there's another way the kernel can be always updated.

Cc: asit.k.mallick@intel.com
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Andi Kleen
2008-01-30 13:32:37 +01:00
committed by Ingo Molnar
parent de4218634e
commit 707fa8ed92
3 changed files with 4 additions and 5 deletions
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3
arch/x86/kernel/cpu/intel.c
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@@ -203,9 +203,10 @@ static void __cpuinit init_intel(struct cpuinfo_x86 *c)
}
#endif
if (cpu_has_xmm)
set_bit(X86_FEATURE_LFENCE_RDTSC, c->x86_capability);
if (c->x86 == 15) {
set_bit(X86_FEATURE_P4, c->x86_capability);
set_bit(X86_FEATURE_SYNC_RDTSC, c->x86_capability);
}
if (c->x86 == 6)
set_bit(X86_FEATURE_P3, c->x86_capability);