From 959b3be64cab9160cd74532a49b89cdd918d38e9 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Thu, 14 Feb 2008 14:56:45 -0800 Subject: [PATCH] x86: don't use P6_NOPs if compiling with CONFIG_X86_GENERIC P6_NOPs are definitely not supported on some VIA CPUs, and possibly (unverified) on AMD K7s. It is also the only thing that prevents a 686 kernel from running on Transmeta TM3x00/5x00 (Crusoe) series. The performance benefit over generic NOPs is very small, so when building for generic consumption, avoid using them. Signed-off-by: H. Peter Anvin Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner --- arch/x86/Kconfig.cpu | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu index 86fd2a0e4597..6d50064db182 100644 --- a/arch/x86/Kconfig.cpu +++ b/arch/x86/Kconfig.cpu @@ -377,9 +377,18 @@ config X86_OOSTORE def_bool y depends on (MWINCHIP3D || MWINCHIP2 || MWINCHIPC6) && MTRR +# +# P6_NOPs are a relatively minor optimization that require a family >= +# 6 processor, except that it is broken on certain VIA chips. +# Furthermore, AMD chips prefer a totally different sequence of NOPs +# (which work on all CPUs). As a result, disallow these if we're +# compiling X86_GENERIC but not X86_64 (these NOPs do work on all +# x86-64 capable chips); the list of processors in the right-hand clause +# are the cores that benefit from this optimization. +# config X86_P6_NOP def_bool y - depends on (M686 || MPENTIUMII || MPENTIUMIII || MPENTIUMM || MCORE2 || PENTIUM4) + depends on (X86_64 || !X86_GENERIC) && (M686 || MPENTIUMII || MPENTIUMIII || MPENTIUMM || MCORE2 || PENTIUM4) config X86_TSC def_bool y -- 2.30.2