From d8d9766c8c29f71c37bc4b74cc9fcf6a192c9bfd Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Mon, 18 Apr 2011 15:31:57 -0700 Subject: [PATCH] x86, cpu: Change NOP selection for certain Intel CPUs Due to a decoder implementation quirk, some specific Intel CPUs actually perform better with the "k8_nops" than with the SDM-recommended NOPs. For runtime-selected NOPs, if we detect those specific CPUs then use the k8_nops instead of the ones we would normally use. Signed-off-by: H. Peter Anvin Cc: Tejun Heo Cc: Steven Rostedt Cc: Frederic Weisbecker Cc: Jason Baron Link: http://lkml.kernel.org/r/1303166160-10315-4-git-send-email-hpa@linux.intel.com --- arch/x86/kernel/alternative.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 846f61eb89c1..c0501ea6b634 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -199,7 +199,19 @@ void __init arch_init_ideal_nops(void) { switch (boot_cpu_data.x86_vendor) { case X86_VENDOR_INTEL: - if (boot_cpu_has(X86_FEATURE_NOPL)) { + /* + * Due to a decoder implementation quirk, some + * specific Intel CPUs actually perform better with + * the "k8_nops" than with the SDM-recommended NOPs. + */ + if (boot_cpu_data.x86 == 6 && + boot_cpu_data.x86_model >= 0x0f && + boot_cpu_data.x86_model != 0x1c && + boot_cpu_data.x86_model != 0x26 && + boot_cpu_data.x86_model != 0x27 && + boot_cpu_data.x86_model < 0x30) { + ideal_nops = k8_nops; + } else if (boot_cpu_has(X86_FEATURE_NOPL)) { ideal_nops = p6_nops; } else { #ifdef CONFIG_X86_64 -- 2.34.1