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Subject[PATCH] [1/3] Provide rdtscll() asm/msr.h for user space
Date

For simple user space timing it's very useful to be able to do
#include <asm/msr.h> instead of having to cut'n'paste the necessarily
macros into all programs. This used to work with older kernels,
but broke with the paravirt support (I ended up with a bunch of
test programs that broke because of that). But it's very useful
to have rdtscll() available somewhere in user space and asm/msr.h
is a good place to have them.

Provide simple rdtsc/rdtscl() macros for user space too in asm/msr.h.
Since they are very simple I don't think they are a burden to maintain.

The diff looks bigger than it is because I moved a code block
and diff doesn't handle it very well.

Signed-off-by: Andi Kleen <ak@linux.intel.com>

Index: linux-2.6.27-rc4-misc/include/asm-x86/msr.h
===================================================================
--- linux-2.6.27-rc4-misc.orig/include/asm-x86/msr.h
+++ linux-2.6.27-rc4-misc/include/asm-x86/msr.h
@@ -4,23 +4,6 @@
#include <asm/msr-index.h>

#ifndef __ASSEMBLY__
-# include <linux/types.h>
-#endif
-
-#ifdef __KERNEL__
-#ifndef __ASSEMBLY__
-
-#include <asm/asm.h>
-#include <asm/errno.h>
-
-static inline unsigned long long native_read_tscp(unsigned int *aux)
-{
- unsigned long low, high;
- asm volatile(".byte 0x0f,0x01,0xf9"
- : "=a" (low), "=d" (high), "=c" (*aux));
- return low | ((u64)high << 32);
-}
-
/*
* i386 calling convention returns 64-bit value in edx:eax, while
* x86_64 returns at rax. Also, the "A" constraint does not really
@@ -29,7 +12,7 @@ static inline unsigned long long native_
*/
#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_VAL(val, low, high) ((low) | ((__u64)(high) << 32))
#define EAX_EDX_ARGS(val, low, high) "a" (low), "d" (high)
#define EAX_EDX_RET(val, low, high) "=a" (low), "=d" (high)
#else
@@ -39,6 +22,23 @@ static inline unsigned long long native_
#define EAX_EDX_RET(val, low, high) "=A" (val)
#endif

+#endif
+
+#ifdef __KERNEL__
+#ifndef __ASSEMBLY__
+
+#include <linux/types.h>
+#include <asm/asm.h>
+#include <asm/errno.h>
+
+static inline unsigned long long native_read_tscp(unsigned int *aux)
+{
+ unsigned long low, high;
+ asm volatile(".byte 0x0f,0x01,0xf9"
+ : "=a" (low), "=d" (high), "=c" (*aux));
+ return low | ((u64)high << 32);
+}
+
static inline unsigned long long native_read_msr(unsigned int msr)
{
DECLARE_ARGS(val, low, high);
@@ -217,6 +217,24 @@ static inline int wrmsr_safe_on_cpu(unsi
}
#endif /* CONFIG_SMP */
#endif /* __ASSEMBLY__ */
+
+#else
+
+/*
+ * Provide simple rdtsc macros for non kernel users. These differ
+ * from the kernel versions by not having barriers and not supporting
+ * paravirtualization.
+ */
+static __always_inline unsigned long long __read_tsc(void)
+{
+ DECLARE_ARGS(val, low, high);
+ asm volatile("rdtsc" : EAX_EDX_RET(val, low, high));
+ return EAX_EDX_VAL(val, low, high);
+}
+
+#define rdtscl(low) ({ asm volatile("rdtsc" : "=a" (low) :: "d"); })
+#define rdtscll(val) ((val) = __read_tsc())
+
#endif /* __KERNEL__ */



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