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x86, cpu: Fix X86_FEATURE_NOPL

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ba0593bf55 cleared the aforementioned
cpuid bit only on 32-bit due to various problems with Virtual PC. This
somehow got lost during the 32- + 64-bit merge so restore the feature
bit on 64-bit. For that, set it explicitly for non-constant arguments of
cpu_has(). Update comment for future reference.

Signed-off-by: Borislav Petkov <bp@alien8.de>
LKML-Reference: <20101004073127.GA20305@liondog.tnic>
Cc: Ryan O'Neill <ryan@innosecc.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
This commit is contained in:
Borislav Petkov 2010-10-04 09:31:27 +02:00 committed by H. Peter Anvin
parent c2b9ff24a0
commit 366d4a43b1
1 changed files with 10 additions and 5 deletions
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15
arch/x86/kernel/cpu/common.c
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@ -704,16 +704,21 @@ void __init early_cpu_init(void)
}
/*
* 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. In the latter case it doesn't even *fail*
* reliably, so probing for it doesn't even work. Disable it completely
* The NOPL instruction is supposed to exist on all CPUs of 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. In the latter case it doesn't even *fail* reliably, so
* probing for it doesn't even work. Disable it completely on 32-bit
* unless we can find a reliable way to detect all the broken cases.
* Enable it explicitly on 64-bit for non-constant inputs of cpu_has().
*/
static void __cpuinit detect_nopl(struct cpuinfo_x86 *c)
{
#ifdef CONFIG_X86_32
clear_cpu_cap(c, X86_FEATURE_NOPL);
#else
set_cpu_cap(c, X86_FEATURE_NOPL);
#endif
}
static void __cpuinit generic_identify(struct cpuinfo_x86 *c)