summaryrefslogtreecommitdiff
path: root/arch/x86/include/asm/msr.h
diff options
context:
space:
mode:
authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-12-15 14:52:16 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2015-12-15 14:52:16 -0300
commit8d91c1e411f55d7ea91b1183a2e9f8088fb4d5be (patch)
treee9891aa6c295060d065adffd610c4f49ecf884f3 /arch/x86/include/asm/msr.h
parenta71852147516bc1cb5b0b3cbd13639bfd4022dc8 (diff)
Linux-libre 4.3.2-gnu
Diffstat (limited to 'arch/x86/include/asm/msr.h')
-rw-r--r--arch/x86/include/asm/msr.h70
1 files changed, 46 insertions, 24 deletions
diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index e6a707eb5..77d8b284e 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -47,14 +47,13 @@ static inline unsigned long long native_read_tscp(unsigned int *aux)
* it means rax *or* rdx.
*/
#ifdef CONFIG_X86_64
-#define DECLARE_ARGS(val, low, high) unsigned low, high
-#define EAX_EDX_VAL(val, low, high) ((low) | ((u64)(high) << 32))
-#define EAX_EDX_ARGS(val, low, high) "a" (low), "d" (high)
+/* Using 64-bit values saves one instruction clearing the high half of low */
+#define DECLARE_ARGS(val, low, high) unsigned long low, high
+#define EAX_EDX_VAL(val, low, high) ((low) | (high) << 32)
#define EAX_EDX_RET(val, low, high) "=a" (low), "=d" (high)
#else
#define DECLARE_ARGS(val, low, high) unsigned long long val
#define EAX_EDX_VAL(val, low, high) (val)
-#define EAX_EDX_ARGS(val, low, high) "A" (val)
#define EAX_EDX_RET(val, low, high) "=A" (val)
#endif
@@ -106,12 +105,19 @@ notrace static inline int native_write_msr_safe(unsigned int msr,
return err;
}
-extern unsigned long long native_read_tsc(void);
-
extern int rdmsr_safe_regs(u32 regs[8]);
extern int wrmsr_safe_regs(u32 regs[8]);
-static __always_inline unsigned long long __native_read_tsc(void)
+/**
+ * rdtsc() - returns the current TSC without ordering constraints
+ *
+ * rdtsc() returns the result of RDTSC as a 64-bit integer. The
+ * only ordering constraint it supplies is the ordering implied by
+ * "asm volatile": it will put the RDTSC in the place you expect. The
+ * CPU can and will speculatively execute that RDTSC, though, so the
+ * results can be non-monotonic if compared on different CPUs.
+ */
+static __always_inline unsigned long long rdtsc(void)
{
DECLARE_ARGS(val, low, high);
@@ -120,6 +126,35 @@ static __always_inline unsigned long long __native_read_tsc(void)
return EAX_EDX_VAL(val, low, high);
}
+/**
+ * rdtsc_ordered() - read the current TSC in program order
+ *
+ * rdtsc_ordered() returns the result of RDTSC as a 64-bit integer.
+ * It is ordered like a load to a global in-memory counter. It should
+ * be impossible to observe non-monotonic rdtsc_unordered() behavior
+ * across multiple CPUs as long as the TSC is synced.
+ */
+static __always_inline unsigned long long rdtsc_ordered(void)
+{
+ /*
+ * The RDTSC instruction is not ordered relative to memory
+ * access. The Intel SDM and the AMD APM are both vague on this
+ * point, but empirically an RDTSC instruction can be
+ * speculatively executed before prior loads. An RDTSC
+ * immediately after an appropriate barrier appears to be
+ * ordered as a normal load, that is, it provides the same
+ * ordering guarantees as reading from a global memory location
+ * that some other imaginary CPU is updating continuously with a
+ * time stamp.
+ */
+ alternative_2("", "mfence", X86_FEATURE_MFENCE_RDTSC,
+ "lfence", X86_FEATURE_LFENCE_RDTSC);
+ return rdtsc();
+}
+
+/* Deprecated, keep it for a cycle for easier merging: */
+#define rdtscll(now) do { (now) = rdtsc_ordered(); } while (0)
+
static inline unsigned long long native_read_pmc(int counter)
{
DECLARE_ARGS(val, low, high);
@@ -153,8 +188,10 @@ static inline void wrmsr(unsigned msr, unsigned low, unsigned high)
#define rdmsrl(msr, val) \
((val) = native_read_msr((msr)))
-#define wrmsrl(msr, val) \
- native_write_msr((msr), (u32)((u64)(val)), (u32)((u64)(val) >> 32))
+static inline void wrmsrl(unsigned msr, u64 val)
+{
+ native_write_msr(msr, (u32)val, (u32)(val >> 32));
+}
/* wrmsr with exception handling */
static inline int wrmsr_safe(unsigned msr, unsigned low, unsigned high)
@@ -180,12 +217,6 @@ static inline int rdmsrl_safe(unsigned msr, unsigned long long *p)
return err;
}
-#define rdtscl(low) \
- ((low) = (u32)__native_read_tsc())
-
-#define rdtscll(val) \
- ((val) = __native_read_tsc())
-
#define rdpmc(counter, low, high) \
do { \
u64 _l = native_read_pmc((counter)); \
@@ -195,15 +226,6 @@ do { \
#define rdpmcl(counter, val) ((val) = native_read_pmc(counter))
-#define rdtscp(low, high, aux) \
-do { \
- unsigned long long _val = native_read_tscp(&(aux)); \
- (low) = (u32)_val; \
- (high) = (u32)(_val >> 32); \
-} while (0)
-
-#define rdtscpll(val, aux) (val) = native_read_tscp(&(aux))
-
#endif /* !CONFIG_PARAVIRT */
/*