x86: add NOPL as a synthetic CPU feature bit

[linux-2.6-omap-h63xx.git] / arch / x86 / kernel / cpu / common_64.c

diff --git a/arch/x86/kernel/cpu/common_64.c b/arch/x86/kernel/cpu/common_64.c
index 7b8cc72feb40e3ed8bfd02437fe3b6324b024f67..c3afba5a81a7bfb1780e715c153349de42106df2 100644 (file)
--- a/arch/x86/kernel/cpu/common_64.c
+++ b/arch/x86/kernel/cpu/common_64.c
@@ -7,19 +7,18 @@
 #include <linux/module.h>
 #include <linux/kgdb.h>
 #include <linux/topology.h>
-#include <linux/string.h>
 #include <linux/delay.h>
 #include <linux/smp.h>
-#include <linux/module.h>
 #include <linux/percpu.h>
-#include <asm/processor.h>
 #include <asm/i387.h>
 #include <asm/msr.h>
 #include <asm/io.h>
+#include <asm/linkage.h>
 #include <asm/mmu_context.h>
 #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>
@@ -217,6 +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)
@@ -305,7 +337,6 @@ static void __cpuinit early_identify_cpu(struct cpuinfo_x86 *c)
                        c->x86_capability[2] = cpuid_edx(0x80860001);
        }
 
-       c->extended_cpuid_level = cpuid_eax(0x80000000);
        if (c->extended_cpuid_level >= 0x80000007)
                c->x86_power = cpuid_edx(0x80000007);
 
@@ -316,18 +347,13 @@ static void __cpuinit early_identify_cpu(struct cpuinfo_x86 *c)
                c->x86_phys_bits = eax & 0xff;
        }
 
-       /* Assume all 64-bit CPUs support 32-bit syscall */
-       set_cpu_cap(c, X86_FEATURE_SYSCALL32);
+       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);
 
        validate_pat_support(c);
-
-       /* early_param could clear that, but recall get it set again */
-       if (disable_apic)
-               clear_cpu_cap(c, X86_FEATURE_APIC);
 }
 
 /*
@@ -517,8 +543,7 @@ void pda_init(int cpu)
 }
 
 char boot_exception_stacks[(N_EXCEPTION_STACKS - 1) * EXCEPTION_STKSZ +
-                          DEBUG_STKSZ]
-__attribute__((section(".bss.page_aligned")));
+                          DEBUG_STKSZ] __page_aligned_bss;
 
 extern asmlinkage void ignore_sysret(void);