Commit 366d4a43 authored by Borislav Petkov's avatar Borislav Petkov Committed by H. Peter Anvin
Browse files

x86, cpu: Fix X86_FEATURE_NOPL 



ba0593bf 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: default avatarBorislav 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: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent c2b9ff24

arch/x86/kernel/cpu/common.c

+10 −5
Original line number Diff line number Diff line
@@ -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)

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