summaryrefslogtreecommitdiff
path: root/arch/x86/kernel/cpu/common.c
diff options
context:
space:
mode:
authorH. Peter Anvin <hpa@zytor.com>2008-09-04 09:04:45 -0700
committerH. Peter Anvin <hpa@zytor.com>2008-09-04 09:04:45 -0700
commitfe47784ba5cbb6b713c013e046859946789b45e4 (patch)
tree6384958d55e29be0d2eb8ae78fa437c10636d8d6 /arch/x86/kernel/cpu/common.c
parent83b8e28b14d63db928cb39e5c5ed2a548246bd71 (diff)
parentaf2e1f276ff08f17192411ea3b71c13a758dfe12 (diff)
Merge branch 'x86/cpu' into x86/xsave
Conflicts: arch/x86/kernel/cpu/feature_names.c include/asm-x86/cpufeature.h
Diffstat (limited to 'arch/x86/kernel/cpu/common.c')
-rw-r--r--arch/x86/kernel/cpu/common.c32
1 files changed, 31 insertions, 1 deletions
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 6c2b9e756db2..c63ec65f484c 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)