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authorH. Peter Anvin <hpa@zytor.com>2008-09-04 08:08:42 -0700
committerH. Peter Anvin <hpa@zytor.com>2008-09-04 08:08:42 -0700
commit7203781c98ad9147564d327de6f6513ad8fc0f4e (patch)
tree5c29a2a04a626bf08a0d56fd8a0068b3c92ad284 /arch/x86/kernel/cpu/common_64.c
parent671eef85a3e885dff4ce210d8774ad50a91d5967 (diff)
parentaf2e1f276ff08f17192411ea3b71c13a758dfe12 (diff)
Merge branch 'x86/cpu' into x86/core
Conflicts: arch/x86/kernel/cpu/feature_names.c include/asm-x86/cpufeature.h
Diffstat (limited to 'arch/x86/kernel/cpu/common_64.c')
-rw-r--r--arch/x86/kernel/cpu/common_64.c36
1 files changed, 36 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/common_64.c b/arch/x86/kernel/cpu/common_64.c
index cc6efe86249..35d11efdf1f 100644
--- a/arch/x86/kernel/cpu/common_64.c
+++ b/arch/x86/kernel/cpu/common_64.c
@@ -18,6 +18,7 @@
#include <asm/mtrr.h>
#include <asm/mce.h>
#include <asm/pat.h>
+#include <asm/asm.h>
#include <asm/numa.h>
#ifdef CONFIG_X86_LOCAL_APIC
#include <asm/mpspec.h>
@@ -215,6 +216,39 @@ static void __init early_cpu_support_print(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. Hence, probe for it based on first
+ * principles.
+ *
+ * Note: no 64-bit chip is known to lack these, but put the code here
+ * for consistency with 32 bits, and to make it utterly trivial to
+ * diagnose the problem should it ever surface.
+ */
+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 early_identify_cpu(struct cpuinfo_x86 *c);
void __init early_cpu_init(void)
@@ -313,6 +347,8 @@ static void __cpuinit early_identify_cpu(struct cpuinfo_x86 *c)
c->x86_phys_bits = eax & 0xff;
}
+ detect_nopl(c);
+
if (c->x86_vendor != X86_VENDOR_UNKNOWN &&
cpu_devs[c->x86_vendor]->c_early_init)
cpu_devs[c->x86_vendor]->c_early_init(c);