Author: Vegard Nossum <vegard.nossum@xxxxxxxxx> AuthorDate: Fri, 20 Feb 2009 13:25:41 +0100 Commit: Vegard Nossum <vegard.nossum@xxxxxxxxx> CommitDate: Sun, 22 Feb 2009 11:54:28 +0100 kmemcheck: disable fast string operations on P4 CPUs This patch may allow us to remove the REP emulation code from kmemcheck. Acked-by: Pekka Enberg <penberg@xxxxxxxxxxxxxx> Signed-off-by: Vegard Nossum <vegard.nossum@xxxxxxxxx> --- arch/x86/kernel/cpu/intel.c | 23 +++++++++++++++++++++++ 1 files changed, 23 insertions(+), 0 deletions(-) diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index 1f137a8..65e9717 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -75,6 +75,29 @@ static void __cpuinit early_init_intel(struct cpuinfo_x86 *c) */ if (c->x86 == 6 && c->x86_model < 15) clear_cpu_cap(c, X86_FEATURE_PAT); + +#ifdef CONFIG_KMEMCHECK + /* + * P4s have a "fast strings" feature which causes single- + * stepping REP instructions to only generate a #DB on + * cache-line boundaries. + * + * Ingo Molnar reported a Pentium D (model 6) and a Xeon + * (model 2) with the same problem. + */ + if (c->x86 == 15) { + u64 misc_enable; + + rdmsrl(MSR_IA32_MISC_ENABLE, misc_enable); + + if (misc_enable & MSR_IA32_MISC_ENABLE_FAST_STRING) { + printk(KERN_INFO "kmemcheck: Disabling fast string operations\n"); + + misc_enable &= ~MSR_IA32_MISC_ENABLE_FAST_STRING; + wrmsrl(MSR_IA32_MISC_ENABLE, misc_enable); + } + } +#endif } #ifdef CONFIG_X86_32 -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html