diff options
author | H. Peter Anvin <hpa@zytor.com> | 2008-08-18 20:39:32 -0400 |
---|---|---|
committer | H. Peter Anvin <hpa@zytor.com> | 2008-09-05 19:13:52 -0400 |
commit | b6734c35af028f06772c0b2c836c7d579e6d4dad (patch) | |
tree | ecdfc0dc851f440b0f5861b8c3fe6b582d516d1b /arch/x86/kernel/cpu/common.c | |
parent | b74b06c5f6612a72298f37baa65460a59c26ca67 (diff) |
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>
Diffstat (limited to 'arch/x86/kernel/cpu/common.c')
-rw-r--r-- | arch/x86/kernel/cpu/common.c | 32 |
1 files changed, 31 insertions, 1 deletions
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 80ab20d4fa39..0785b3c8d043 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c | |||
@@ -13,6 +13,7 @@ | |||
13 | #include <asm/mtrr.h> | 13 | #include <asm/mtrr.h> |
14 | #include <asm/mce.h> | 14 | #include <asm/mce.h> |
15 | #include <asm/pat.h> | 15 | #include <asm/pat.h> |
16 | #include <asm/asm.h> | ||
16 | #ifdef CONFIG_X86_LOCAL_APIC | 17 | #ifdef CONFIG_X86_LOCAL_APIC |
17 | #include <asm/mpspec.h> | 18 | #include <asm/mpspec.h> |
18 | #include <asm/apic.h> | 19 | #include <asm/apic.h> |
@@ -341,6 +342,35 @@ static void __init early_cpu_detect(void) | |||
341 | early_get_cap(c); | 342 | early_get_cap(c); |
342 | } | 343 | } |
343 | 344 | ||
345 | /* | ||
346 | * The NOPL instruction is supposed to exist on all CPUs with | ||
347 | * family >= 6, unfortunately, that's not true in practice because | ||
348 | * of early VIA chips and (more importantly) broken virtualizers that | ||
349 | * are not easy to detect. Hence, probe for it based on first | ||
350 | * principles. | ||
351 | */ | ||
352 | static void __cpuinit detect_nopl(struct cpuinfo_x86 *c) | ||
353 | { | ||
354 | const u32 nopl_signature = 0x888c53b1; /* Random number */ | ||
355 | u32 has_nopl = nopl_signature; | ||
356 | |||
357 | clear_cpu_cap(c, X86_FEATURE_NOPL); | ||
358 | if (c->x86 >= 6) { | ||
359 | asm volatile("\n" | ||
360 | "1: .byte 0x0f,0x1f,0xc0\n" /* nopl %eax */ | ||
361 | "2:\n" | ||
362 | " .section .fixup,\"ax\"\n" | ||
363 | "3: xor %0,%0\n" | ||
364 | " jmp 2b\n" | ||
365 | " .previous\n" | ||
366 | _ASM_EXTABLE(1b,3b) | ||
367 | : "+a" (has_nopl)); | ||
368 | |||
369 | if (has_nopl == nopl_signature) | ||
370 | set_cpu_cap(c, X86_FEATURE_NOPL); | ||
371 | } | ||
372 | } | ||
373 | |||
344 | static void __cpuinit generic_identify(struct cpuinfo_x86 *c) | 374 | static void __cpuinit generic_identify(struct cpuinfo_x86 *c) |
345 | { | 375 | { |
346 | u32 tfms, xlvl; | 376 | u32 tfms, xlvl; |
@@ -395,8 +425,8 @@ static void __cpuinit generic_identify(struct cpuinfo_x86 *c) | |||
395 | } | 425 | } |
396 | 426 | ||
397 | init_scattered_cpuid_features(c); | 427 | init_scattered_cpuid_features(c); |
428 | detect_nopl(c); | ||
398 | } | 429 | } |
399 | |||
400 | } | 430 | } |
401 | 431 | ||
402 | static void __cpuinit squash_the_stupid_serial_number(struct cpuinfo_x86 *c) | 432 | static void __cpuinit squash_the_stupid_serial_number(struct cpuinfo_x86 *c) |