diff options
| author | H. Peter Anvin <hpa@zytor.com> | 2008-09-16 09:29:40 -0700 |
|---|---|---|
| committer | H. Peter Anvin <hpa@zytor.com> | 2008-09-16 09:33:57 -0700 |
| commit | ba0593bf553c450a03dbc5f8c1f0ff58b778a0c8 (patch) | |
| tree | 027517cfd97e0ddc3513273a1dcb92d00db38234 /arch/x86 | |
| parent | 5132895f14a57607152f7865dc862fb076ce2585 (diff) | |
x86: completely disable NOPL on 32 bits
Completely disable NOPL on 32 bits. It turns out that Microsoft
Virtual PC is so broken it can't even reliably *fail* in the presence
of NOPL.
This leaves the infrastructure in place but disables it
unconditionally.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/kernel/cpu/common.c | 24 |
1 files changed, 4 insertions, 20 deletions
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 8aab8517642..4e456bd955b 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -344,31 +344,15 @@ static void __init early_cpu_detect(void) /* * The NOPL instruction is supposed to exist on all CPUs with - * family >= 6, unfortunately, that's not true in practice because + * 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. + * are not easy to detect. In the latter case it doesn't even *fail* + * reliably, so probing for it doesn't even work. Disable it completely + * unless we can find a reliable way to detect all the broken cases. */ 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) |