From: H. Peter Anvin Date: Tue, 19 Aug 2008 00:39:32 +0000 (-0700) Subject: x86: add NOPL as a synthetic CPU feature bit X-Git-Tag: v2.6.27-rc6~23^2~6 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b6734c35af028f06772c0b2c836c7d579e6d4dad;p=linux-2.6 x86: add NOPL as a synthetic CPU feature bit The long noops ("NOPL") are supposed to be detected by family >= 6. Unfortunately, several non-Intel x86 implementations, both hardware and software, don't obey this dictum. Instead, probe for NOPL directly by executing a NOPL instruction and see if we get #UD. Signed-off-by: H. Peter Anvin --- diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 80ab20d4fa..0785b3c8d0 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -13,6 +13,7 @@ #include #include #include +#include #ifdef CONFIG_X86_LOCAL_APIC #include #include @@ -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) diff --git a/arch/x86/kernel/cpu/common_64.c b/arch/x86/kernel/cpu/common_64.c index dd6e3f1501..c3afba5a81 100644 --- a/arch/x86/kernel/cpu/common_64.c +++ b/arch/x86/kernel/cpu/common_64.c @@ -18,6 +18,7 @@ #include #include #include +#include #include #ifdef CONFIG_X86_LOCAL_APIC #include @@ -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); diff --git a/arch/x86/kernel/cpu/feature_names.c b/arch/x86/kernel/cpu/feature_names.c index e43ad4ad4c..c901779949 100644 --- a/arch/x86/kernel/cpu/feature_names.c +++ b/arch/x86/kernel/cpu/feature_names.c @@ -39,7 +39,8 @@ const char * const x86_cap_flags[NCAPINTS*32] = { NULL, NULL, NULL, NULL, "constant_tsc", "up", NULL, "arch_perfmon", "pebs", "bts", NULL, NULL, - "rep_good", NULL, NULL, NULL, NULL, NULL, NULL, NULL, + "rep_good", NULL, NULL, NULL, + "nopl", NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, /* Intel-defined (#2) */ diff --git a/include/asm-x86/cpufeature.h b/include/asm-x86/cpufeature.h index 762f6a6bc7..9489283a4b 100644 --- a/include/asm-x86/cpufeature.h +++ b/include/asm-x86/cpufeature.h @@ -72,14 +72,15 @@ #define X86_FEATURE_UP (3*32+ 9) /* smp kernel running on up */ #define X86_FEATURE_FXSAVE_LEAK (3*32+10) /* FXSAVE leaks FOP/FIP/FOP */ #define X86_FEATURE_ARCH_PERFMON (3*32+11) /* Intel Architectural PerfMon */ -#define X86_FEATURE_PEBS (3*32+12) /* Precise-Event Based Sampling */ -#define X86_FEATURE_BTS (3*32+13) /* Branch Trace Store */ -#define X86_FEATURE_SYSCALL32 (3*32+14) /* syscall in ia32 userspace */ -#define X86_FEATURE_SYSENTER32 (3*32+15) /* sysenter in ia32 userspace */ +#define X86_FEATURE_PEBS (3*32+12) /* Precise-Event Based Sampling */ +#define X86_FEATURE_BTS (3*32+13) /* Branch Trace Store */ +#define X86_FEATURE_SYSCALL32 (3*32+14) /* syscall in ia32 userspace */ +#define X86_FEATURE_SYSENTER32 (3*32+15) /* sysenter in ia32 userspace */ #define X86_FEATURE_REP_GOOD (3*32+16) /* rep microcode works well on this CPU */ #define X86_FEATURE_MFENCE_RDTSC (3*32+17) /* Mfence synchronizes RDTSC */ #define X86_FEATURE_LFENCE_RDTSC (3*32+18) /* Lfence synchronizes RDTSC */ -#define X86_FEATURE_11AP (3*32+19) /* Bad local APIC aka 11AP */ +#define X86_FEATURE_11AP (3*32+19) /* Bad local APIC aka 11AP */ +#define X86_FEATURE_NOPL (3*32+20) /* The NOPL (0F 1F) instructions */ /* Intel-defined CPU features, CPUID level 0x00000001 (ecx), word 4 */ #define X86_FEATURE_XMM3 (4*32+ 0) /* Streaming SIMD Extensions-3 */ diff --git a/include/asm-x86/required-features.h b/include/asm-x86/required-features.h index adec887dd7..5c2ff4bc29 100644 --- a/include/asm-x86/required-features.h +++ b/include/asm-x86/required-features.h @@ -41,6 +41,12 @@ # define NEED_3DNOW 0 #endif +#if defined(CONFIG_X86_P6_NOP) || defined(CONFIG_X86_64) +# define NEED_NOPL (1<<(X86_FEATURE_NOPL & 31)) +#else +# define NEED_NOPL 0 +#endif + #ifdef CONFIG_X86_64 #define NEED_PSE 0 #define NEED_MSR (1<<(X86_FEATURE_MSR & 31)) @@ -67,7 +73,7 @@ #define REQUIRED_MASK1 (NEED_LM|NEED_3DNOW) #define REQUIRED_MASK2 0 -#define REQUIRED_MASK3 0 +#define REQUIRED_MASK3 (NEED_NOPL) #define REQUIRED_MASK4 0 #define REQUIRED_MASK5 0 #define REQUIRED_MASK6 0