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 <hpa@zytor.com>
This commit is contained in:
H. Peter Anvin 2008-08-18 17:39:32 -07:00
parent b74b06c5f6
commit b6734c35af
5 changed files with 82 additions and 8 deletions

View File

@ -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)

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@ -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);

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@ -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) */

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@ -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 */

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@ -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