diff options
| author | Christoph Lameter <cl@linux.com> | 2011-03-12 14:50:10 +0300 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2011-03-29 12:18:30 +0400 |
| commit | 349c004e3d31fda23ad225b61861be38047fff16 (patch) | |
| tree | 1600c1356f4b992d07e191492054619d03e7c9f7 /arch/x86/include/asm | |
| parent | 89078d572eb9ce8d4c04264b8b0ba86de0d74c8f (diff) | |
| download | linux-349c004e3d31fda23ad225b61861be38047fff16.tar.xz | |
x86: A fast way to check capabilities of the current cpu
Add this_cpu_has() which determines if the current cpu has a certain
ability using a segment prefix and a bit test operation.
For that we need to add bit operations to x86s percpu.h.
Many uses of cpu_has use a pointer passed to a function to determine
the current flags. That is no longer necessary after this patch.
However, this patch only converts the straightforward cases where
cpu_has is used with this_cpu_ptr. The rest is work for later.
-tj: Rolled up patch to add x86_ prefix and use percpu_read() instead
of percpu_read_stable().
Signed-off-by: Christoph Lameter <cl@linux.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'arch/x86/include/asm')
| -rw-r--r-- | arch/x86/include/asm/cpufeature.h | 13 | ||||
| -rw-r--r-- | arch/x86/include/asm/percpu.h | 27 |
2 files changed, 36 insertions, 4 deletions
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h index 91f3e087cf21..50c0d30e676d 100644 --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -207,8 +207,7 @@ extern const char * const x86_power_flags[32]; #define test_cpu_cap(c, bit) \ test_bit(bit, (unsigned long *)((c)->x86_capability)) -#define cpu_has(c, bit) \ - (__builtin_constant_p(bit) && \ +#define REQUIRED_MASK_BIT_SET(bit) \ ( (((bit)>>5)==0 && (1UL<<((bit)&31) & REQUIRED_MASK0)) || \ (((bit)>>5)==1 && (1UL<<((bit)&31) & REQUIRED_MASK1)) || \ (((bit)>>5)==2 && (1UL<<((bit)&31) & REQUIRED_MASK2)) || \ @@ -218,10 +217,16 @@ extern const char * const x86_power_flags[32]; (((bit)>>5)==6 && (1UL<<((bit)&31) & REQUIRED_MASK6)) || \ (((bit)>>5)==7 && (1UL<<((bit)&31) & REQUIRED_MASK7)) || \ (((bit)>>5)==8 && (1UL<<((bit)&31) & REQUIRED_MASK8)) || \ - (((bit)>>5)==9 && (1UL<<((bit)&31) & REQUIRED_MASK9)) ) \ - ? 1 : \ + (((bit)>>5)==9 && (1UL<<((bit)&31) & REQUIRED_MASK9)) ) + +#define cpu_has(c, bit) \ + (__builtin_constant_p(bit) && REQUIRED_MASK_BIT_SET(bit) ? 1 : \ test_cpu_cap(c, bit)) +#define this_cpu_has(bit) \ + (__builtin_constant_p(bit) && REQUIRED_MASK_BIT_SET(bit) ? 1 : \ + x86_this_cpu_test_bit(bit, (unsigned long *)&cpu_info.x86_capability)) + #define boot_cpu_has(bit) cpu_has(&boot_cpu_data, bit) #define set_cpu_cap(c, bit) set_bit(bit, (unsigned long *)((c)->x86_capability)) diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h index d475b4398d8b..76042d981596 100644 --- a/arch/x86/include/asm/percpu.h +++ b/arch/x86/include/asm/percpu.h @@ -542,6 +542,33 @@ do { \ old__; \ }) +static __always_inline int x86_this_cpu_constant_test_bit(unsigned int nr, + const unsigned long __percpu *addr) +{ + unsigned long __percpu *a = (unsigned long *)addr + nr / BITS_PER_LONG; + + return ((1UL << (nr % BITS_PER_LONG)) & percpu_read(*a)) != 0; +} + +static inline int x86_this_cpu_variable_test_bit(int nr, + const unsigned long __percpu *addr) +{ + int oldbit; + + asm volatile("bt "__percpu_arg(2)",%1\n\t" + "sbb %0,%0" + : "=r" (oldbit) + : "m" (*(unsigned long *)addr), "Ir" (nr)); + + return oldbit; +} + +#define x86_this_cpu_test_bit(nr, addr) \ + (__builtin_constant_p((nr)) \ + ? x86_this_cpu_constant_test_bit((nr), (addr)) \ + : x86_this_cpu_variable_test_bit((nr), (addr))) + + #include <asm-generic/percpu.h> /* We can use this directly for local CPU (faster). */ |