diff options
author | H. Peter Anvin <hpa@zytor.com> | 2008-08-18 17:39:32 -0700 |
---|---|---|
committer | H. Peter Anvin <hpa@zytor.com> | 2008-08-18 18:22:17 -0700 |
commit | 7e00df5818964298c9821365a6cb7a8304227c5c (patch) | |
tree | 5fdfc9a40deb0a4157bddffed28322a2ff9e5875 /arch/x86/kernel/cpu/common.c | |
parent | e2fe16d91228a005811335fbc4fbad5d4f5b75af (diff) | |
download | op-kernel-dev-7e00df5818964298c9821365a6cb7a8304227c5c.zip op-kernel-dev-7e00df5818964298c9821365a6cb7a8304227c5c.tar.gz |
x86: add NOPL as a synthetic CPU feature bit
The long noops ("NOPL") are supposed to be detected by family >= 6.
Unfortunately, several non-Intel x86 implementations, both hardware
and software, don't obey this dictum. Instead, probe for NOPL
directly by executing a NOPL instruction and see if we get #UD.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'arch/x86/kernel/cpu/common.c')
-rw-r--r-- | arch/x86/kernel/cpu/common.c | 32 |
1 files changed, 31 insertions, 1 deletions
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 80ab20d..0785b3c 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -13,6 +13,7 @@ #include <asm/mtrr.h> #include <asm/mce.h> #include <asm/pat.h> +#include <asm/asm.h> #ifdef CONFIG_X86_LOCAL_APIC #include <asm/mpspec.h> #include <asm/apic.h> @@ -341,6 +342,35 @@ static void __init early_cpu_detect(void) early_get_cap(c); } +/* + * The NOPL instruction is supposed to exist on all CPUs with + * family >= 6, unfortunately, that's not true in practice because + * of early VIA chips and (more importantly) broken virtualizers that + * are not easy to detect. Hence, probe for it based on first + * principles. + */ +static void __cpuinit detect_nopl(struct cpuinfo_x86 *c) +{ + const u32 nopl_signature = 0x888c53b1; /* Random number */ + u32 has_nopl = nopl_signature; + + clear_cpu_cap(c, X86_FEATURE_NOPL); + if (c->x86 >= 6) { + asm volatile("\n" + "1: .byte 0x0f,0x1f,0xc0\n" /* nopl %eax */ + "2:\n" + " .section .fixup,\"ax\"\n" + "3: xor %0,%0\n" + " jmp 2b\n" + " .previous\n" + _ASM_EXTABLE(1b,3b) + : "+a" (has_nopl)); + + if (has_nopl == nopl_signature) + set_cpu_cap(c, X86_FEATURE_NOPL); + } +} + static void __cpuinit generic_identify(struct cpuinfo_x86 *c) { u32 tfms, xlvl; @@ -395,8 +425,8 @@ static void __cpuinit generic_identify(struct cpuinfo_x86 *c) } init_scattered_cpuid_features(c); + detect_nopl(c); } - } static void __cpuinit squash_the_stupid_serial_number(struct cpuinfo_x86 *c) |