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| author | H. Peter Anvin <hpa@linux.intel.com> | 2011-04-19 00:31:57 +0200 |
|---|---|---|
| committer | H. Peter Anvin <hpa@linux.intel.com> | 2011-04-19 01:40:32 +0200 |
| commit | d8d9766c8c29f71c37bc4b74cc9fcf6a192c9bfd (patch) | |
| tree | e491da1e7e5a7dd2b500d4cb62b17b56e13f306a /arch/x86/kernel/alternative.c | |
| parent | x86, cpu: Clean up and unify the NOP selection infrastructure (diff) | |
| download | linux-d8d9766c8c29f71c37bc4b74cc9fcf6a192c9bfd.tar.xz linux-d8d9766c8c29f71c37bc4b74cc9fcf6a192c9bfd.zip | |
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 <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
Diffstat (limited to 'arch/x86/kernel/alternative.c')
| -rw-r--r-- | arch/x86/kernel/alternative.c | 14 |
1 files changed, 13 insertions, 1 deletions
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 |