Commit d8d9766c authored by H. Peter Anvin's avatar H. Peter Anvin

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: default avatarH. Peter Anvin <hpa@linux.intel.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jason Baron <jbaron@redhat.com>
Link: http://lkml.kernel.org/r/1303166160-10315-4-git-send-email-hpa@linux.intel.com
parent dc326fca
......@@ -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
......
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