Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

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

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

arch/x86/kernel/alternative.c

+13 −1
Original line number Diff line number Diff line
@@ -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