[PATCH v2 00/17] x86/tsc: Clean up rdtsc helpers

[PATCH v2 00/17] x86/tsc: Clean up rdtsc helpers

[Andy Lutomirski]

My sincere apologies for the spam.  I send an unholy mixture of the
real patch set and an old poorly split-up patch set, and the result
is incomprehensible.  Here's what I meant to send.

After the some recent threads about rdtsc barriers, I remembered
that our RDTSC wrappers are a big mess.  Let's clean it up.

Currently we have rdtscl, rdtscll, native_read_tsc,
paravirt_read_tsc, and rdtsc_barrier.  For people who haven't
noticed rdtsc_barrier and who haven't carefully read the docs,
there's no indication that all of the other accessors have a giant
ordering gotcha.  The macro forms are ugly, and the paravirt
implementation is completely pointless.

rdtscl is particularly awful.  It reads the low bits.  There are no
performance critical users of just the low bits anywhere in the
kernel.

Clean it up.  After this patch set, there are exactly three
functions.  rdtsc_unordered() is a function that does a raw RDTSC
and returns a 64-bit number.  rdtsc_ordered() is a function that
does a properly ordered RDTSC for general-purpose use.
barrier_before_rdtsc() is exactly what it sounds like.

Andy Lutomirski (17):
  x86/tsc: Inline native_read_tsc and remove __native_read_tsc
  x86/msr/kvm: Remove vget_cycles()
  x86/tsc/paravirt: Remove the read_tsc and read_tscp paravirt hooks
  x86/tsc: Replace rdtscll with native_read_tsc
  x86/tsc: Remove the rdtscp and rdtscpll macros
  x86/tsc: Use the full 64-bit tsc in tsc_delay
  x86/cpu/amd: Use the full 64-bit TSC to detect the 2.6.2 bug
  baycom_epp: Replace rdtscl() with native_read_tsc()
  staging/lirc_serial: Remove TSC-based timing
  input/joystick/analog: Switch from rdtscl() to native_read_tsc()
  drivers/input/gameport: Replace rdtscl() with native_read_tsc()
  x86/tsc: Remove rdtscl()
  x86/tsc: Rename native_read_tsc() to rdtsc_unordered()
  x86/tsc: Move rdtsc_barrier() and rename it to barrier_before_rdtsc()
  x86: Add rdtsc_ordered() and use it in trivial call sites
  x86/tsc: Use rdtsc_ordered() in check_tsc_warp() and drop extra
    barriers
  x86/tsc: In read_tsc, use rdtsc_ordered() instead of get_cycles()

 arch/x86/boot/compressed/aslr.c                    |  2 +-
 arch/x86/entry/vdso/vclock_gettime.c               | 16 +-----
 arch/x86/include/asm/barrier.h                     | 11 ----
 arch/x86/include/asm/msr.h                         | 63 +++++++++++++++-------
 arch/x86/include/asm/paravirt.h                    | 34 ------------
 arch/x86/include/asm/paravirt_types.h              |  2 -
 arch/x86/include/asm/pvclock.h                     |  8 +--
 arch/x86/include/asm/stackprotector.h              |  2 +-
 arch/x86/include/asm/tsc.h                         | 18 +------
 arch/x86/kernel/apb_timer.c                        |  8 +--
 arch/x86/kernel/apic/apic.c                        |  8 +--
 arch/x86/kernel/cpu/amd.c                          |  6 +--
 arch/x86/kernel/cpu/mcheck/mce.c                   |  4 +-
 arch/x86/kernel/espfix_64.c                        |  2 +-
 arch/x86/kernel/hpet.c                             |  4 +-
 arch/x86/kernel/paravirt.c                         |  2 -
 arch/x86/kernel/paravirt_patch_32.c                |  2 -
 arch/x86/kernel/trace_clock.c                      |  7 +--
 arch/x86/kernel/tsc.c                              | 12 ++---
 arch/x86/kernel/tsc_sync.c                         | 14 +++--
 arch/x86/kvm/lapic.c                               |  4 +-
 arch/x86/kvm/svm.c                                 |  4 +-
 arch/x86/kvm/vmx.c                                 |  4 +-
 arch/x86/kvm/x86.c                                 | 26 +++------
 arch/x86/lib/delay.c                               | 13 ++---
 arch/x86/um/asm/barrier.h                          |  4 +-
 arch/x86/xen/enlighten.c                           |  3 --
 drivers/input/gameport/gameport.c                  |  4 +-
 drivers/input/joystick/analog.c                    |  4 +-
 drivers/net/hamradio/baycom_epp.c                  |  2 +-
 drivers/staging/media/lirc/lirc_serial.c           | 63 ++--------------------
 drivers/thermal/intel_powerclamp.c                 |  4 +-
 .../power/cpupower/debug/kernel/cpufreq-test_tsc.c |  4 +-
 33 files changed, 112 insertions(+), 252 deletions(-)

-- 
2.4.2

[PATCH v2 01/17] x86/tsc: Inline native_read_tsc and remove __native_read_tsc

[Andy Lutomirski]

In cdc7957d1954 ("x86: move native_read_tsc() offline"),
native_read_tsc was moved out of line, presumably for some
now-obsolete vDSO-related reason.  Undo it.

The entire rdtsc, shl, or sequence is only 11 bytes, and calls via
rdtscl and similar helpers were already inlined.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/entry/vdso/vclock_gettime.c  | 2 +-
 arch/x86/include/asm/msr.h            | 8 +++-----
 arch/x86/include/asm/pvclock.h        | 2 +-
 arch/x86/include/asm/stackprotector.h | 2 +-
 arch/x86/include/asm/tsc.h            | 2 +-
 arch/x86/kernel/apb_timer.c           | 4 ++--
 arch/x86/kernel/tsc.c                 | 6 ------
 7 files changed, 9 insertions(+), 17 deletions(-)

diff --git a/arch/x86/entry/vdso/vclock_gettime.c b/arch/x86/entry/vdso/vclock_gettime.c
index 9793322751e0..972b488ac16a 100644
--- a/arch/x86/entry/vdso/vclock_gettime.c
+++ b/arch/x86/entry/vdso/vclock_gettime.c
@@ -186,7 +186,7 @@ notrace static cycle_t vread_tsc(void)
 	 * but no one has ever seen it happen.
 	 */
 	rdtsc_barrier();
-	ret = (cycle_t)__native_read_tsc();
+	ret = (cycle_t)native_read_tsc();
 
 	last = gtod->cycle_last;
 
diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index e6a707eb5081..88711470af7f 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -106,12 +106,10 @@ 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)
+static __always_inline unsigned long long native_read_tsc(void)
 {
 	DECLARE_ARGS(val, low, high);
 
@@ -181,10 +179,10 @@ static inline int rdmsrl_safe(unsigned msr, unsigned long long *p)
 }
 
 #define rdtscl(low)						\
-	((low) = (u32)__native_read_tsc())
+	((low) = (u32)native_read_tsc())
 
 #define rdtscll(val)						\
-	((val) = __native_read_tsc())
+	((val) = native_read_tsc())
 
 #define rdpmc(counter, low, high)			\
 do {							\
diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h
index d6b078e9fa28..71bd485c2986 100644
--- a/arch/x86/include/asm/pvclock.h
+++ b/arch/x86/include/asm/pvclock.h
@@ -62,7 +62,7 @@ static inline u64 pvclock_scale_delta(u64 delta, u32 mul_frac, int shift)
 static __always_inline
 u64 pvclock_get_nsec_offset(const struct pvclock_vcpu_time_info *src)
 {
-	u64 delta = __native_read_tsc() - src->tsc_timestamp;
+	u64 delta = native_read_tsc() - src->tsc_timestamp;
 	return pvclock_scale_delta(delta, src->tsc_to_system_mul,
 				   src->tsc_shift);
 }
diff --git a/arch/x86/include/asm/stackprotector.h b/arch/x86/include/asm/stackprotector.h
index c2e00bb2a136..bc5fa2af112e 100644
--- a/arch/x86/include/asm/stackprotector.h
+++ b/arch/x86/include/asm/stackprotector.h
@@ -72,7 +72,7 @@ static __always_inline void boot_init_stack_canary(void)
 	 * on during the bootup the random pool has true entropy too.
 	 */
 	get_random_bytes(&canary, sizeof(canary));
-	tsc = __native_read_tsc();
+	tsc = native_read_tsc();
 	canary += tsc + (tsc << 32UL);
 
 	current->stack_canary = canary;
diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h
index 94605c0e9cee..fd11128faf25 100644
--- a/arch/x86/include/asm/tsc.h
+++ b/arch/x86/include/asm/tsc.h
@@ -42,7 +42,7 @@ static __always_inline cycles_t vget_cycles(void)
 	if (!cpu_has_tsc)
 		return 0;
 #endif
-	return (cycles_t)__native_read_tsc();
+	return (cycles_t)native_read_tsc();
 }
 
 extern void tsc_init(void);
diff --git a/arch/x86/kernel/apb_timer.c b/arch/x86/kernel/apb_timer.c
index ede92c3364d3..9fe111cc50f8 100644
--- a/arch/x86/kernel/apb_timer.c
+++ b/arch/x86/kernel/apb_timer.c
@@ -390,13 +390,13 @@ unsigned long apbt_quick_calibrate(void)
 	old = dw_apb_clocksource_read(clocksource_apbt);
 	old += loop;
 
-	t1 = __native_read_tsc();
+	t1 = native_read_tsc();
 
 	do {
 		new = dw_apb_clocksource_read(clocksource_apbt);
 	} while (new < old);
 
-	t2 = __native_read_tsc();
+	t2 = native_read_tsc();
 
 	shift = 5;
 	if (unlikely(loop >> shift == 0)) {
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 505449700e0c..e7710cd7ba00 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -308,12 +308,6 @@ unsigned long long
 sched_clock(void) __attribute__((alias("native_sched_clock")));
 #endif
 
-unsigned long long native_read_tsc(void)
-{
-	return __native_read_tsc();
-}
-EXPORT_SYMBOL(native_read_tsc);
-
 int check_tsc_unstable(void)
 {
 	return tsc_unstable;
-- 
2.4.2

[PATCH v2 02/17] x86/msr/kvm: Remove vget_cycles()

[Andy Lutomirski]

The only caller was kvm's read_tsc.  The only difference between
vget_cycles and native_read_tsc was that vget_cycles returned zero
instead of crashing on TSC-less systems.  KVM's already checks
vclock_mode before calling that function, so the extra check is
unnecessary.

(Off-topic, but the whole KVM clock host implementation is gross.
 IMO it should be rewritten.)

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/include/asm/tsc.h | 13 -------------
 arch/x86/kvm/x86.c         |  2 +-
 2 files changed, 1 insertion(+), 14 deletions(-)

diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h
index fd11128faf25..3da1cc1218ac 100644
--- a/arch/x86/include/asm/tsc.h
+++ b/arch/x86/include/asm/tsc.h
@@ -32,19 +32,6 @@ static inline cycles_t get_cycles(void)
 	return ret;
 }
 
-static __always_inline cycles_t vget_cycles(void)
-{
-	/*
-	 * We only do VDSOs on TSC capable CPUs, so this shouldn't
-	 * access boot_cpu_data (which is not VDSO-safe):
-	 */
-#ifndef CONFIG_X86_TSC
-	if (!cpu_has_tsc)
-		return 0;
-#endif
-	return (cycles_t)native_read_tsc();
-}
-
 extern void tsc_init(void);
 extern void mark_tsc_unstable(char *reason);
 extern int unsynchronized_tsc(void);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 26eaeb522cab..c26faf408bce 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1430,7 +1430,7 @@ static cycle_t read_tsc(void)
 	 * but no one has ever seen it happen.
 	 */
 	rdtsc_barrier();
-	ret = (cycle_t)vget_cycles();
+	ret = (cycle_t)native_read_tsc();
 
 	last = pvclock_gtod_data.clock.cycle_last;
 
-- 
2.4.2

[PATCH v2 03/17] x86/tsc/paravirt: Remove the read_tsc and read_tscp paravirt hooks

[Andy Lutomirski]

We've had read_tsc and read_tscp paravirt hooks since the very
beginning of paravirt, i.e., d3561b7fa0fb ("[PATCH] paravirt: header
and stubs for paravirtualisation").  AFAICT the only paravirt guest
implementation that ever replaced these calls was vmware, and it's
gone.  Arguably even vmware shouldn't have hooked rdtsc -- we fully
support systems that don't have a TSC at all, so there's no point
for a paravirt implementation to pretend that we have a TSC but to
replace it.

I also doubt that these hooks actually worked.  Calls to rdtscl and
rdtscll, which respected the hooks, were used seemingly
interchangeably with native_read_tsc, which did not.

Just remove them.  If anyone ever needs them again, they can try
to make a case for why they need them.

Before, on a paravirt config:
   text	   data	    bss	    dec	    hex	filename
13426505	1827056	14508032	29761593	1c62039	vmlinux

After:
   text	   data	    bss	    dec	    hex	filename
13426617	1827056	14508032	29761705	1c620a9	vmlinux

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/include/asm/msr.h            | 16 ++++++++--------
 arch/x86/include/asm/paravirt.h       | 34 ----------------------------------
 arch/x86/include/asm/paravirt_types.h |  2 --
 arch/x86/kernel/paravirt.c            |  2 --
 arch/x86/kernel/paravirt_patch_32.c   |  2 --
 arch/x86/xen/enlighten.c              |  3 ---
 6 files changed, 8 insertions(+), 51 deletions(-)

diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index 88711470af7f..d1afac7df484 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -178,12 +178,6 @@ 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));		\
@@ -193,6 +187,14 @@ do {							\
 
 #define rdpmcl(counter, val) ((val) = native_read_pmc(counter))
 
+#endif	/* !CONFIG_PARAVIRT */
+
+#define rdtscl(low)						\
+	((low) = (u32)native_read_tsc())
+
+#define rdtscll(val)						\
+	((val) = native_read_tsc())
+
 #define rdtscp(low, high, aux)					\
 do {                                                            \
 	unsigned long long _val = native_read_tscp(&(aux));     \
@@ -202,8 +204,6 @@ do {                                                            \
 
 #define rdtscpll(val, aux) (val) = native_read_tscp(&(aux))
 
-#endif	/* !CONFIG_PARAVIRT */
-
 /*
  * 64-bit version of wrmsr_safe():
  */
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index d143bfad45d7..c2be0375bcad 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -174,19 +174,6 @@ static inline int rdmsrl_safe(unsigned msr, unsigned long long *p)
 	return err;
 }
 
-static inline u64 paravirt_read_tsc(void)
-{
-	return PVOP_CALL0(u64, pv_cpu_ops.read_tsc);
-}
-
-#define rdtscl(low)				\
-do {						\
-	u64 _l = paravirt_read_tsc();		\
-	low = (int)_l;				\
-} while (0)
-
-#define rdtscll(val) (val = paravirt_read_tsc())
-
 static inline unsigned long long paravirt_sched_clock(void)
 {
 	return PVOP_CALL0(unsigned long long, pv_time_ops.sched_clock);
@@ -215,27 +202,6 @@ do {						\
 
 #define rdpmcl(counter, val) ((val) = paravirt_read_pmc(counter))
 
-static inline unsigned long long paravirt_rdtscp(unsigned int *aux)
-{
-	return PVOP_CALL1(u64, pv_cpu_ops.read_tscp, aux);
-}
-
-#define rdtscp(low, high, aux)				\
-do {							\
-	int __aux;					\
-	unsigned long __val = paravirt_rdtscp(&__aux);	\
-	(low) = (u32)__val;				\
-	(high) = (u32)(__val >> 32);			\
-	(aux) = __aux;					\
-} while (0)
-
-#define rdtscpll(val, aux)				\
-do {							\
-	unsigned long __aux; 				\
-	val = paravirt_rdtscp(&__aux);			\
-	(aux) = __aux;					\
-} while (0)
-
 static inline void paravirt_alloc_ldt(struct desc_struct *ldt, unsigned entries)
 {
 	PVOP_VCALL2(pv_cpu_ops.alloc_ldt, ldt, entries);
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index a6b8f9fadb06..ce029e4fa7c6 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -156,9 +156,7 @@ struct pv_cpu_ops {
 	u64 (*read_msr)(unsigned int msr, int *err);
 	int (*write_msr)(unsigned int msr, unsigned low, unsigned high);
 
-	u64 (*read_tsc)(void);
 	u64 (*read_pmc)(int counter);
-	unsigned long long (*read_tscp)(unsigned int *aux);
 
 #ifdef CONFIG_X86_32
 	/*
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index 58bcfb67c01f..f68e48f5f6c2 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -351,9 +351,7 @@ __visible struct pv_cpu_ops pv_cpu_ops = {
 	.wbinvd = native_wbinvd,
 	.read_msr = native_read_msr_safe,
 	.write_msr = native_write_msr_safe,
-	.read_tsc = native_read_tsc,
 	.read_pmc = native_read_pmc,
-	.read_tscp = native_read_tscp,
 	.load_tr_desc = native_load_tr_desc,
 	.set_ldt = native_set_ldt,
 	.load_gdt = native_load_gdt,
diff --git a/arch/x86/kernel/paravirt_patch_32.c b/arch/x86/kernel/paravirt_patch_32.c
index e1b013696dde..c89f50a76e97 100644
--- a/arch/x86/kernel/paravirt_patch_32.c
+++ b/arch/x86/kernel/paravirt_patch_32.c
@@ -10,7 +10,6 @@ DEF_NATIVE(pv_mmu_ops, read_cr2, "mov %cr2, %eax");
 DEF_NATIVE(pv_mmu_ops, write_cr3, "mov %eax, %cr3");
 DEF_NATIVE(pv_mmu_ops, read_cr3, "mov %cr3, %eax");
 DEF_NATIVE(pv_cpu_ops, clts, "clts");
-DEF_NATIVE(pv_cpu_ops, read_tsc, "rdtsc");
 
 #if defined(CONFIG_PARAVIRT_SPINLOCKS) && defined(CONFIG_QUEUED_SPINLOCKS)
 DEF_NATIVE(pv_lock_ops, queued_spin_unlock, "movb $0, (%eax)");
@@ -52,7 +51,6 @@ unsigned native_patch(u8 type, u16 clobbers, void *ibuf,
 		PATCH_SITE(pv_mmu_ops, read_cr3);
 		PATCH_SITE(pv_mmu_ops, write_cr3);
 		PATCH_SITE(pv_cpu_ops, clts);
-		PATCH_SITE(pv_cpu_ops, read_tsc);
 #if defined(CONFIG_PARAVIRT_SPINLOCKS) && defined(CONFIG_QUEUED_SPINLOCKS)
 		case PARAVIRT_PATCH(pv_lock_ops.queued_spin_unlock):
 			if (pv_is_native_spin_unlock()) {
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 0b95c9b8283f..32136bfca43f 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1175,11 +1175,8 @@ static const struct pv_cpu_ops xen_cpu_ops __initconst = {
 	.read_msr = xen_read_msr_safe,
 	.write_msr = xen_write_msr_safe,
 
-	.read_tsc = native_read_tsc,
 	.read_pmc = native_read_pmc,
 
-	.read_tscp = native_read_tscp,
-
 	.iret = xen_iret,
 #ifdef CONFIG_X86_64
 	.usergs_sysret32 = xen_sysret32,
-- 
2.4.2

[PATCH v2 04/17] x86/tsc: Replace rdtscll with native_read_tsc

[Andy Lutomirski]

Now that the read_tsc paravirt hook is gone, rdtscll() is just a
wrapper around native_read_tsc().  Unwrap it.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/boot/compressed/aslr.c                      | 2 +-
 arch/x86/include/asm/msr.h                           | 3 ---
 arch/x86/include/asm/tsc.h                           | 5 +----
 arch/x86/kernel/apb_timer.c                          | 4 ++--
 arch/x86/kernel/apic/apic.c                          | 8 ++++----
 arch/x86/kernel/cpu/mcheck/mce.c                     | 4 ++--
 arch/x86/kernel/espfix_64.c                          | 2 +-
 arch/x86/kernel/hpet.c                               | 4 ++--
 arch/x86/kernel/trace_clock.c                        | 2 +-
 arch/x86/kernel/tsc.c                                | 4 ++--
 arch/x86/kvm/vmx.c                                   | 2 +-
 arch/x86/lib/delay.c                                 | 2 +-
 drivers/thermal/intel_powerclamp.c                   | 4 ++--
 tools/power/cpupower/debug/kernel/cpufreq-test_tsc.c | 4 ++--
 14 files changed, 22 insertions(+), 28 deletions(-)

diff --git a/arch/x86/boot/compressed/aslr.c b/arch/x86/boot/compressed/aslr.c
index d7b1f655b3ef..ea33236190b1 100644
--- a/arch/x86/boot/compressed/aslr.c
+++ b/arch/x86/boot/compressed/aslr.c
@@ -82,7 +82,7 @@ static unsigned long get_random_long(void)
 
 	if (has_cpuflag(X86_FEATURE_TSC)) {
 		debug_putstr(" RDTSC");
-		rdtscll(raw);
+		raw = native_read_tsc();
 
 		random ^= raw;
 		use_i8254 = false;
diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index d1afac7df484..7273b74e0f99 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -192,9 +192,6 @@ do {							\
 #define rdtscl(low)						\
 	((low) = (u32)native_read_tsc())
 
-#define rdtscll(val)						\
-	((val) = native_read_tsc())
-
 #define rdtscp(low, high, aux)					\
 do {                                                            \
 	unsigned long long _val = native_read_tscp(&(aux));     \
diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h
index 3da1cc1218ac..b4883902948b 100644
--- a/arch/x86/include/asm/tsc.h
+++ b/arch/x86/include/asm/tsc.h
@@ -21,15 +21,12 @@ extern void disable_TSC(void);
 
 static inline cycles_t get_cycles(void)
 {
-	unsigned long long ret = 0;
-
 #ifndef CONFIG_X86_TSC
 	if (!cpu_has_tsc)
 		return 0;
 #endif
-	rdtscll(ret);
 
-	return ret;
+	return native_read_tsc();
 }
 
 extern void tsc_init(void);
diff --git a/arch/x86/kernel/apb_timer.c b/arch/x86/kernel/apb_timer.c
index 9fe111cc50f8..25efa534c4e4 100644
--- a/arch/x86/kernel/apb_timer.c
+++ b/arch/x86/kernel/apb_timer.c
@@ -263,7 +263,7 @@ static int apbt_clocksource_register(void)
 
 	/* Verify whether apbt counter works */
 	t1 = dw_apb_clocksource_read(clocksource_apbt);
-	rdtscll(start);
+	start = native_read_tsc();
 
 	/*
 	 * We don't know the TSC frequency yet, but waiting for
@@ -273,7 +273,7 @@ static int apbt_clocksource_register(void)
 	 */
 	do {
 		rep_nop();
-		rdtscll(now);
+		now = native_read_tsc();
 	} while ((now - start) < 200000UL);
 
 	/* APBT is the only always on clocksource, it has to work! */
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index dcb52850a28f..51af1ed1ae2e 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -457,7 +457,7 @@ static int lapic_next_deadline(unsigned long delta,
 {
 	u64 tsc;
 
-	rdtscll(tsc);
+	tsc = native_read_tsc();
 	wrmsrl(MSR_IA32_TSC_DEADLINE, tsc + (((u64) delta) * TSC_DIVISOR));
 	return 0;
 }
@@ -592,7 +592,7 @@ static void __init lapic_cal_handler(struct clock_event_device *dev)
 	unsigned long pm = acpi_pm_read_early();
 
 	if (cpu_has_tsc)
-		rdtscll(tsc);
+		tsc = native_read_tsc();
 
 	switch (lapic_cal_loops++) {
 	case 0:
@@ -1209,7 +1209,7 @@ void setup_local_APIC(void)
 	long long max_loops = cpu_khz ? cpu_khz : 1000000;
 
 	if (cpu_has_tsc)
-		rdtscll(tsc);
+		tsc = native_read_tsc();
 
 	if (disable_apic) {
 		disable_ioapic_support();
@@ -1293,7 +1293,7 @@ void setup_local_APIC(void)
 		}
 		if (queued) {
 			if (cpu_has_tsc && cpu_khz) {
-				rdtscll(ntsc);
+				ntsc = native_read_tsc();
 				max_loops = (cpu_khz << 10) - (ntsc - tsc);
 			} else
 				max_loops--;
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index df919ff103c3..a5283d2d0094 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -125,7 +125,7 @@ void mce_setup(struct mce *m)
 {
 	memset(m, 0, sizeof(struct mce));
 	m->cpu = m->extcpu = smp_processor_id();
-	rdtscll(m->tsc);
+	m->tsc = native_read_tsc();
 	/* We hope get_seconds stays lockless */
 	m->time = get_seconds();
 	m->cpuvendor = boot_cpu_data.x86_vendor;
@@ -1784,7 +1784,7 @@ static void collect_tscs(void *data)
 {
 	unsigned long *cpu_tsc = (unsigned long *)data;
 
-	rdtscll(cpu_tsc[smp_processor_id()]);
+	cpu_tsc[smp_processor_id()] = native_read_tsc();
 }
 
 static int mce_apei_read_done;
diff --git a/arch/x86/kernel/espfix_64.c b/arch/x86/kernel/espfix_64.c
index f5d0730e7b08..334a2a9c034d 100644
--- a/arch/x86/kernel/espfix_64.c
+++ b/arch/x86/kernel/espfix_64.c
@@ -110,7 +110,7 @@ static void init_espfix_random(void)
 	 */
 	if (!arch_get_random_long(&rand)) {
 		/* The constant is an arbitrary large prime */
-		rdtscll(rand);
+		rand = native_read_tsc();
 		rand *= 0xc345c6b72fd16123UL;
 	}
 
diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index e2449cf38b06..ccf677cd9adc 100644
--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -734,7 +734,7 @@ static int hpet_clocksource_register(void)
 
 	/* Verify whether hpet counter works */
 	t1 = hpet_readl(HPET_COUNTER);
-	rdtscll(start);
+	start = native_read_tsc();
 
 	/*
 	 * We don't know the TSC frequency yet, but waiting for
@@ -744,7 +744,7 @@ static int hpet_clocksource_register(void)
 	 */
 	do {
 		rep_nop();
-		rdtscll(now);
+		now = native_read_tsc();
 	} while ((now - start) < 200000UL);
 
 	if (t1 == hpet_readl(HPET_COUNTER)) {
diff --git a/arch/x86/kernel/trace_clock.c b/arch/x86/kernel/trace_clock.c
index 25b993729f9b..bd8f4d41bd56 100644
--- a/arch/x86/kernel/trace_clock.c
+++ b/arch/x86/kernel/trace_clock.c
@@ -15,7 +15,7 @@ u64 notrace trace_clock_x86_tsc(void)
 	u64 ret;
 
 	rdtsc_barrier();
-	rdtscll(ret);
+	ret = native_read_tsc();
 
 	return ret;
 }
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index e7710cd7ba00..e66f5dcaeb63 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -248,7 +248,7 @@ static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
 
 	data = cyc2ns_write_begin(cpu);
 
-	rdtscll(tsc_now);
+	tsc_now = native_read_tsc();
 	ns_now = cycles_2_ns(tsc_now);
 
 	/*
@@ -290,7 +290,7 @@ u64 native_sched_clock(void)
 	}
 
 	/* read the Time Stamp Counter: */
-	rdtscll(tsc_now);
+	tsc_now = native_read_tsc();
 
 	/* return the value in ns */
 	return cycles_2_ns(tsc_now);
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index e11dd59398f1..fcff42100948 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2236,7 +2236,7 @@ static u64 guest_read_tsc(void)
 {
 	u64 host_tsc, tsc_offset;
 
-	rdtscll(host_tsc);
+	host_tsc = native_read_tsc();
 	tsc_offset = vmcs_read64(TSC_OFFSET);
 	return host_tsc + tsc_offset;
 }
diff --git a/arch/x86/lib/delay.c b/arch/x86/lib/delay.c
index 39d6a3db0b96..9a52ad0c0758 100644
--- a/arch/x86/lib/delay.c
+++ b/arch/x86/lib/delay.c
@@ -100,7 +100,7 @@ void use_tsc_delay(void)
 int read_current_timer(unsigned long *timer_val)
 {
 	if (delay_fn == delay_tsc) {
-		rdtscll(*timer_val);
+		*timer_val = native_read_tsc();
 		return 0;
 	}
 	return -1;
diff --git a/drivers/thermal/intel_powerclamp.c b/drivers/thermal/intel_powerclamp.c
index 725718e97a0b..933c5e599d1d 100644
--- a/drivers/thermal/intel_powerclamp.c
+++ b/drivers/thermal/intel_powerclamp.c
@@ -340,7 +340,7 @@ static bool powerclamp_adjust_controls(unsigned int target_ratio,
 
 	/* check result for the last window */
 	msr_now = pkg_state_counter();
-	rdtscll(tsc_now);
+	tsc_now = native_read_tsc();
 
 	/* calculate pkg cstate vs tsc ratio */
 	if (!msr_last || !tsc_last)
@@ -482,7 +482,7 @@ static void poll_pkg_cstate(struct work_struct *dummy)
 	u64 val64;
 
 	msr_now = pkg_state_counter();
-	rdtscll(tsc_now);
+	tsc_now = native_read_tsc();
 	jiffies_now = jiffies;
 
 	/* calculate pkg cstate vs tsc ratio */
diff --git a/tools/power/cpupower/debug/kernel/cpufreq-test_tsc.c b/tools/power/cpupower/debug/kernel/cpufreq-test_tsc.c
index 5224ee5b392d..f02b0c0bff9b 100644
--- a/tools/power/cpupower/debug/kernel/cpufreq-test_tsc.c
+++ b/tools/power/cpupower/debug/kernel/cpufreq-test_tsc.c
@@ -81,11 +81,11 @@ static int __init cpufreq_test_tsc(void)
 
 	printk(KERN_DEBUG "start--> \n");
 	then = read_pmtmr();
-        rdtscll(then_tsc);
+	then_tsc = native_read_tsc();
 	for (i=0;i<20;i++) {
 		mdelay(100);
 		now = read_pmtmr();
-		rdtscll(now_tsc);
+		now_tsc = native_read_tsc();
 		diff = (now - then) & 0xFFFFFF;
 		diff_tsc = now_tsc - then_tsc;
 		printk(KERN_DEBUG "t1: %08u t2: %08u diff_pmtmr: %08u diff_tsc: %016llu\n", then, now, diff, diff_tsc);
-- 
2.4.2

[PATCH v2 05/17] x86/tsc: Remove the rdtscp and rdtscpll macros

[Andy Lutomirski]

They have no users.  Leave native_read_tscp, which seems potentially
useful despite also having no callers.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/include/asm/msr.h | 9 ---------
 1 file changed, 9 deletions(-)

diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index 7273b74e0f99..626f78199665 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -192,15 +192,6 @@ do {							\
 #define rdtscl(low)						\
 	((low) = (u32)native_read_tsc())
 
-#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))
-
 /*
  * 64-bit version of wrmsr_safe():
  */
-- 
2.4.2

[PATCH v2 06/17] x86/tsc: Use the full 64-bit tsc in tsc_delay

[Andy Lutomirski]

As a very minor optimization, tsc_delay was only using the low 32
bits of the TSC.  It's a delay function, so just use the whole
thing.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/lib/delay.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/lib/delay.c b/arch/x86/lib/delay.c
index 9a52ad0c0758..35115f3786a9 100644
--- a/arch/x86/lib/delay.c
+++ b/arch/x86/lib/delay.c
@@ -49,16 +49,16 @@ static void delay_loop(unsigned long loops)
 /* TSC based delay: */
 static void delay_tsc(unsigned long __loops)
 {
-	u32 bclock, now, loops = __loops;
+	u64 bclock, now, loops = __loops;
 	int cpu;
 
 	preempt_disable();
 	cpu = smp_processor_id();
 	rdtsc_barrier();
-	rdtscl(bclock);
+	bclock = native_read_tsc();
 	for (;;) {
 		rdtsc_barrier();
-		rdtscl(now);
+		now = native_read_tsc();
 		if ((now - bclock) >= loops)
 			break;
 
@@ -80,7 +80,7 @@ static void delay_tsc(unsigned long __loops)
 			loops -= (now - bclock);
 			cpu = smp_processor_id();
 			rdtsc_barrier();
-			rdtscl(bclock);
+			bclock = native_read_tsc();
 		}
 	}
 	preempt_enable();
-- 
2.4.2

[PATCH v2 07/17] x86/cpu/amd: Use the full 64-bit TSC to detect the 2.6.2 bug

[Andy Lutomirski]

This code is timing 100k indirect calls, so the added overhead of
counting the number of cycles elapsed as a 64-bit number should be
insignificant.  Drop the optimization of using a 32-bit count.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/kernel/cpu/amd.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 5bd3a99dc20b..c5ceec532799 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -107,7 +107,7 @@ static void init_amd_k6(struct cpuinfo_x86 *c)
 		const int K6_BUG_LOOP = 1000000;
 		int n;
 		void (*f_vide)(void);
-		unsigned long d, d2;
+		u64 d, d2;
 
 		printk(KERN_INFO "AMD K6 stepping B detected - ");
 
@@ -118,10 +118,10 @@ static void init_amd_k6(struct cpuinfo_x86 *c)
 
 		n = K6_BUG_LOOP;
 		f_vide = vide;
-		rdtscl(d);
+		d = native_read_tsc();
 		while (n--)
 			f_vide();
-		rdtscl(d2);
+		d2 = native_read_tsc();
 		d = d2-d;
 
 		if (d > 20*K6_BUG_LOOP)
-- 
2.4.2

[PATCH v2 08/17] baycom_epp: Replace rdtscl() with native_read_tsc()

[Andy Lutomirski]

This is only used if BAYCOM_DEBUG is defined.

Cc: Thomas Sailer <t.sailer@alumni.ethz.ch>
Cc: linux-hams@vger.kernel.org
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 drivers/net/hamradio/baycom_epp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/hamradio/baycom_epp.c b/drivers/net/hamradio/baycom_epp.c
index 83c7cce0d172..44e5c3b5e0af 100644
--- a/drivers/net/hamradio/baycom_epp.c
+++ b/drivers/net/hamradio/baycom_epp.c
@@ -638,7 +638,7 @@ static int receive(struct net_device *dev, int cnt)
 #define GETTICK(x)                                                \
 ({                                                                \
 	if (cpu_has_tsc)                                          \
-		rdtscl(x);                                        \
+		x = (unsigned int)native_read_tsc();		  \
 })
 #else /* __i386__ */
 #define GETTICK(x)
-- 
2.4.2

Re: [PATCH v2 08/17] baycom_epp: Replace rdtscl() with native_read_tsc()

[walter harms]

Hello,
please add a line what is the difference between V1 and V2.

re,
 wh

Am 13.06.2015 01:44, schrieb Andy Lutomirski:
> This is only used if BAYCOM_DEBUG is defined.
> 
> Cc: Thomas Sailer <t.sailer@alumni.ethz.ch>
> Cc: linux-hams@vger.kernel.org
> Signed-off-by: Andy Lutomirski <luto@kernel.org>
> ---
>  drivers/net/hamradio/baycom_epp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/hamradio/baycom_epp.c b/drivers/net/hamradio/baycom_epp.c
> index 83c7cce0d172..44e5c3b5e0af 100644
> --- a/drivers/net/hamradio/baycom_epp.c
> +++ b/drivers/net/hamradio/baycom_epp.c
> @@ -638,7 +638,7 @@ static int receive(struct net_device *dev, int cnt)
>  #define GETTICK(x)                                                \
>  ({                                                                \
>  	if (cpu_has_tsc)                                          \
> -		rdtscl(x);                                        \
> +		x = (unsigned int)native_read_tsc();		  \
>  })
>  #else /* __i386__ */
>  #define GETTICK(x)

Re: [PATCH v2 08/17] baycom_epp: Replace rdtscl() with native_read_tsc()

[Andy Lutomirski]

On Sat, Jun 13, 2015 at 3:45 AM, walter harms <wharms@bfs.de> wrote:
> Hello,
> please add a line what is the difference between V1 and V2.
>

There is none.  v1 was screwed up elsewhere in the series.

This is part of a larger series to clean up the rdtsc inlines and
macros.  I'm hoping for an ack so this can go in through -tip.

Thanks,
Andy

> re,
>  wh
>
> Am 13.06.2015 01:44, schrieb Andy Lutomirski:
>> This is only used if BAYCOM_DEBUG is defined.
>>
>> Cc: Thomas Sailer <t.sailer@alumni.ethz.ch>
>> Cc: linux-hams@vger.kernel.org
>> Signed-off-by: Andy Lutomirski <luto@kernel.org>
>> ---
>>  drivers/net/hamradio/baycom_epp.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/hamradio/baycom_epp.c b/drivers/net/hamradio/baycom_epp.c
>> index 83c7cce0d172..44e5c3b5e0af 100644
>> --- a/drivers/net/hamradio/baycom_epp.c
>> +++ b/drivers/net/hamradio/baycom_epp.c
>> @@ -638,7 +638,7 @@ static int receive(struct net_device *dev, int cnt)
>>  #define GETTICK(x)                                                \
>>  ({                                                                \
>>       if (cpu_has_tsc)                                          \
>> -             rdtscl(x);                                        \
>> +             x = (unsigned int)native_read_tsc();              \
>>  })
>>  #else /* __i386__ */
>>  #define GETTICK(x)



-- 
Andy Lutomirski
AMA Capital Management, LLC

[PATCH v2 09/17] staging/lirc_serial: Remove TSC-based timing

[Andy Lutomirski]

It wasn't compiled in by default.  I suspect that the driver was and
still is broken, though -- it's calling udelay with a parameter
that's derived from loops_per_jiffy.

Cc: Jarod Wilson <jarod@wilsonet.com>
Cc: devel@driverdev.osuosl.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 drivers/staging/media/lirc/lirc_serial.c | 63 ++------------------------------
 1 file changed, 4 insertions(+), 59 deletions(-)

diff --git a/drivers/staging/media/lirc/lirc_serial.c b/drivers/staging/media/lirc/lirc_serial.c
index dc7984455c3a..465796a686c4 100644
--- a/drivers/staging/media/lirc/lirc_serial.c
+++ b/drivers/staging/media/lirc/lirc_serial.c
@@ -327,9 +327,6 @@ static void safe_udelay(unsigned long usecs)
  * time
  */
 
-/* So send_pulse can quickly convert microseconds to clocks */
-static unsigned long conv_us_to_clocks;
-
 static int init_timing_params(unsigned int new_duty_cycle,
 		unsigned int new_freq)
 {
@@ -344,7 +341,6 @@ static int init_timing_params(unsigned int new_duty_cycle,
 	/* How many clocks in a microsecond?, avoiding long long divide */
 	work = loops_per_sec;
 	work *= 4295;  /* 4295 = 2^32 / 1e6 */
-	conv_us_to_clocks = work >> 32;
 
 	/*
 	 * Carrier period in clocks, approach good up to 32GHz clock,
@@ -357,10 +353,9 @@ static int init_timing_params(unsigned int new_duty_cycle,
 	pulse_width = period * duty_cycle / 100;
 	space_width = period - pulse_width;
 	dprintk("in init_timing_params, freq=%d, duty_cycle=%d, "
-		"clk/jiffy=%ld, pulse=%ld, space=%ld, "
-		"conv_us_to_clocks=%ld\n",
+		"clk/jiffy=%ld, pulse=%ld, space=%ld\n",
 		freq, duty_cycle, __this_cpu_read(cpu_info.loops_per_jiffy),
-		pulse_width, space_width, conv_us_to_clocks);
+		pulse_width, space_width);
 	return 0;
 }
 #else /* ! USE_RDTSC */
@@ -431,63 +426,14 @@ static long send_pulse_irdeo(unsigned long length)
 	return ret;
 }
 
-#ifdef USE_RDTSC
-/* Version that uses Pentium rdtsc instruction to measure clocks */
-
-/*
- * This version does sub-microsecond timing using rdtsc instruction,
- * and does away with the fudged LIRC_SERIAL_TRANSMITTER_LATENCY
- * Implicitly i586 architecture...  - Steve
- */
-
-static long send_pulse_homebrew_softcarrier(unsigned long length)
-{
-	int flag;
-	unsigned long target, start, now;
-
-	/* Get going quick as we can */
-	rdtscl(start);
-	on();
-	/* Convert length from microseconds to clocks */
-	length *= conv_us_to_clocks;
-	/* And loop till time is up - flipping at right intervals */
-	now = start;
-	target = pulse_width;
-	flag = 1;
-	/*
-	 * FIXME: This looks like a hard busy wait, without even an occasional,
-	 * polite, cpu_relax() call.  There's got to be a better way?
-	 *
-	 * The i2c code has the result of a lot of bit-banging work, I wonder if
-	 * there's something there which could be helpful here.
-	 */
-	while ((now - start) < length) {
-		/* Delay till flip time */
-		do {
-			rdtscl(now);
-		} while ((now - start) < target);
-
-		/* flip */
-		if (flag) {
-			rdtscl(now);
-			off();
-			target += space_width;
-		} else {
-			rdtscl(now); on();
-			target += pulse_width;
-		}
-		flag = !flag;
-	}
-	rdtscl(now);
-	return ((now - start) - length) / conv_us_to_clocks;
-}
-#else /* ! USE_RDTSC */
 /* Version using udelay() */
 
 /*
  * here we use fixed point arithmetic, with 8
  * fractional bits.  that gets us within 0.1% or so of the right average
  * frequency, albeit with some jitter in pulse length - Steve
+ *
+ * This should use ndelay instead.
  */
 
 /* To match 8 fractional bits used for pulse/space length */
@@ -520,7 +466,6 @@ static long send_pulse_homebrew_softcarrier(unsigned long length)
 	}
 	return (actual-length) >> 8;
 }
-#endif /* USE_RDTSC */
 
 static long send_pulse_homebrew(unsigned long length)
 {
-- 
2.4.2

Re: [PATCH v2 09/17] staging/lirc_serial: Remove TSC-based timing

[Dan Carpenter]

This one should go to Mauro and linux-media@vger.kernel.org instead of
Greg and devel@driverdev.osuosl.org.

regards,
dan carpenter

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Re: [PATCH v2 09/17] staging/lirc_serial: Remove TSC-based timing

[Andy Lutomirski]

Hi Mauro, etc:

Are you okay with this change landing in the tip tree?

--Andy

On Fri, Jun 12, 2015 at 4:44 PM, Andy Lutomirski <luto@kernel.org> wrote:
> It wasn't compiled in by default.  I suspect that the driver was and
> still is broken, though -- it's calling udelay with a parameter
> that's derived from loops_per_jiffy.
>
> Cc: Jarod Wilson <jarod@wilsonet.com>
> Cc: devel@driverdev.osuosl.org
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Andy Lutomirski <luto@kernel.org>
> ---
>  drivers/staging/media/lirc/lirc_serial.c | 63 ++------------------------------
>  1 file changed, 4 insertions(+), 59 deletions(-)
>
> diff --git a/drivers/staging/media/lirc/lirc_serial.c b/drivers/staging/media/lirc/lirc_serial.c
> index dc7984455c3a..465796a686c4 100644
> --- a/drivers/staging/media/lirc/lirc_serial.c
> +++ b/drivers/staging/media/lirc/lirc_serial.c
> @@ -327,9 +327,6 @@ static void safe_udelay(unsigned long usecs)
>   * time
>   */
>
> -/* So send_pulse can quickly convert microseconds to clocks */
> -static unsigned long conv_us_to_clocks;
> -
>  static int init_timing_params(unsigned int new_duty_cycle,
>                 unsigned int new_freq)
>  {
> @@ -344,7 +341,6 @@ static int init_timing_params(unsigned int new_duty_cycle,
>         /* How many clocks in a microsecond?, avoiding long long divide */
>         work = loops_per_sec;
>         work *= 4295;  /* 4295 = 2^32 / 1e6 */
> -       conv_us_to_clocks = work >> 32;
>
>         /*
>          * Carrier period in clocks, approach good up to 32GHz clock,
> @@ -357,10 +353,9 @@ static int init_timing_params(unsigned int new_duty_cycle,
>         pulse_width = period * duty_cycle / 100;
>         space_width = period - pulse_width;
>         dprintk("in init_timing_params, freq=%d, duty_cycle=%d, "
> -               "clk/jiffy=%ld, pulse=%ld, space=%ld, "
> -               "conv_us_to_clocks=%ld\n",
> +               "clk/jiffy=%ld, pulse=%ld, space=%ld\n",
>                 freq, duty_cycle, __this_cpu_read(cpu_info.loops_per_jiffy),
> -               pulse_width, space_width, conv_us_to_clocks);
> +               pulse_width, space_width);
>         return 0;
>  }
>  #else /* ! USE_RDTSC */
> @@ -431,63 +426,14 @@ static long send_pulse_irdeo(unsigned long length)
>         return ret;
>  }
>
> -#ifdef USE_RDTSC
> -/* Version that uses Pentium rdtsc instruction to measure clocks */
> -
> -/*
> - * This version does sub-microsecond timing using rdtsc instruction,
> - * and does away with the fudged LIRC_SERIAL_TRANSMITTER_LATENCY
> - * Implicitly i586 architecture...  - Steve
> - */
> -
> -static long send_pulse_homebrew_softcarrier(unsigned long length)
> -{
> -       int flag;
> -       unsigned long target, start, now;
> -
> -       /* Get going quick as we can */
> -       rdtscl(start);
> -       on();
> -       /* Convert length from microseconds to clocks */
> -       length *= conv_us_to_clocks;
> -       /* And loop till time is up - flipping at right intervals */
> -       now = start;
> -       target = pulse_width;
> -       flag = 1;
> -       /*
> -        * FIXME: This looks like a hard busy wait, without even an occasional,
> -        * polite, cpu_relax() call.  There's got to be a better way?
> -        *
> -        * The i2c code has the result of a lot of bit-banging work, I wonder if
> -        * there's something there which could be helpful here.
> -        */
> -       while ((now - start) < length) {
> -               /* Delay till flip time */
> -               do {
> -                       rdtscl(now);
> -               } while ((now - start) < target);
> -
> -               /* flip */
> -               if (flag) {
> -                       rdtscl(now);
> -                       off();
> -                       target += space_width;
> -               } else {
> -                       rdtscl(now); on();
> -                       target += pulse_width;
> -               }
> -               flag = !flag;
> -       }
> -       rdtscl(now);
> -       return ((now - start) - length) / conv_us_to_clocks;
> -}
> -#else /* ! USE_RDTSC */
>  /* Version using udelay() */
>
>  /*
>   * here we use fixed point arithmetic, with 8
>   * fractional bits.  that gets us within 0.1% or so of the right average
>   * frequency, albeit with some jitter in pulse length - Steve
> + *
> + * This should use ndelay instead.
>   */
>
>  /* To match 8 fractional bits used for pulse/space length */
> @@ -520,7 +466,6 @@ static long send_pulse_homebrew_softcarrier(unsigned long length)
>         }
>         return (actual-length) >> 8;
>  }
> -#endif /* USE_RDTSC */
>
>  static long send_pulse_homebrew(unsigned long length)
>  {
> --
> 2.4.2
>



-- 
Andy Lutomirski
AMA Capital Management, LLC
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Re: [PATCH v2 09/17] staging/lirc_serial: Remove TSC-based timing

[Andy Lutomirski]

Hi Mauro, etc:

Are you okay with this change landing in the tip tree?

--Andy

On Fri, Jun 12, 2015 at 4:44 PM, Andy Lutomirski <luto@kernel.org> wrote:
> It wasn't compiled in by default.  I suspect that the driver was and
> still is broken, though -- it's calling udelay with a parameter
> that's derived from loops_per_jiffy.
>
> Cc: Jarod Wilson <jarod@wilsonet.com>
> Cc: devel@driverdev.osuosl.org
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Andy Lutomirski <luto@kernel.org>
> ---
>  drivers/staging/media/lirc/lirc_serial.c | 63 ++------------------------------
>  1 file changed, 4 insertions(+), 59 deletions(-)
>
> diff --git a/drivers/staging/media/lirc/lirc_serial.c b/drivers/staging/media/lirc/lirc_serial.c
> index dc7984455c3a..465796a686c4 100644
> --- a/drivers/staging/media/lirc/lirc_serial.c
> +++ b/drivers/staging/media/lirc/lirc_serial.c
> @@ -327,9 +327,6 @@ static void safe_udelay(unsigned long usecs)
>   * time
>   */
>
> -/* So send_pulse can quickly convert microseconds to clocks */
> -static unsigned long conv_us_to_clocks;
> -
>  static int init_timing_params(unsigned int new_duty_cycle,
>                 unsigned int new_freq)
>  {
> @@ -344,7 +341,6 @@ static int init_timing_params(unsigned int new_duty_cycle,
>         /* How many clocks in a microsecond?, avoiding long long divide */
>         work = loops_per_sec;
>         work *= 4295;  /* 4295 = 2^32 / 1e6 */
> -       conv_us_to_clocks = work >> 32;
>
>         /*
>          * Carrier period in clocks, approach good up to 32GHz clock,
> @@ -357,10 +353,9 @@ static int init_timing_params(unsigned int new_duty_cycle,
>         pulse_width = period * duty_cycle / 100;
>         space_width = period - pulse_width;
>         dprintk("in init_timing_params, freq=%d, duty_cycle=%d, "
> -               "clk/jiffy=%ld, pulse=%ld, space=%ld, "
> -               "conv_us_to_clocks=%ld\n",
> +               "clk/jiffy=%ld, pulse=%ld, space=%ld\n",
>                 freq, duty_cycle, __this_cpu_read(cpu_info.loops_per_jiffy),
> -               pulse_width, space_width, conv_us_to_clocks);
> +               pulse_width, space_width);
>         return 0;
>  }
>  #else /* ! USE_RDTSC */
> @@ -431,63 +426,14 @@ static long send_pulse_irdeo(unsigned long length)
>         return ret;
>  }
>
> -#ifdef USE_RDTSC
> -/* Version that uses Pentium rdtsc instruction to measure clocks */
> -
> -/*
> - * This version does sub-microsecond timing using rdtsc instruction,
> - * and does away with the fudged LIRC_SERIAL_TRANSMITTER_LATENCY
> - * Implicitly i586 architecture...  - Steve
> - */
> -
> -static long send_pulse_homebrew_softcarrier(unsigned long length)
> -{
> -       int flag;
> -       unsigned long target, start, now;
> -
> -       /* Get going quick as we can */
> -       rdtscl(start);
> -       on();
> -       /* Convert length from microseconds to clocks */
> -       length *= conv_us_to_clocks;
> -       /* And loop till time is up - flipping at right intervals */
> -       now = start;
> -       target = pulse_width;
> -       flag = 1;
> -       /*
> -        * FIXME: This looks like a hard busy wait, without even an occasional,
> -        * polite, cpu_relax() call.  There's got to be a better way?
> -        *
> -        * The i2c code has the result of a lot of bit-banging work, I wonder if
> -        * there's something there which could be helpful here.
> -        */
> -       while ((now - start) < length) {
> -               /* Delay till flip time */
> -               do {
> -                       rdtscl(now);
> -               } while ((now - start) < target);
> -
> -               /* flip */
> -               if (flag) {
> -                       rdtscl(now);
> -                       off();
> -                       target += space_width;
> -               } else {
> -                       rdtscl(now); on();
> -                       target += pulse_width;
> -               }
> -               flag = !flag;
> -       }
> -       rdtscl(now);
> -       return ((now - start) - length) / conv_us_to_clocks;
> -}
> -#else /* ! USE_RDTSC */
>  /* Version using udelay() */
>
>  /*
>   * here we use fixed point arithmetic, with 8
>   * fractional bits.  that gets us within 0.1% or so of the right average
>   * frequency, albeit with some jitter in pulse length - Steve
> + *
> + * This should use ndelay instead.
>   */
>
>  /* To match 8 fractional bits used for pulse/space length */
> @@ -520,7 +466,6 @@ static long send_pulse_homebrew_softcarrier(unsigned long length)
>         }
>         return (actual-length) >> 8;
>  }
> -#endif /* USE_RDTSC */
>
>  static long send_pulse_homebrew(unsigned long length)
>  {
> --
> 2.4.2
>



-- 
Andy Lutomirski
AMA Capital Management, LLC
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[PATCH v2 10/17] input/joystick/analog: Switch from rdtscl() to native_read_tsc()

[Andy Lutomirski]

This timing code is hideous, and this doesn't help.  It gets rid of
one of the last users of rdtscl, though.

Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: linux-input@vger.kernel.org
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 drivers/input/joystick/analog.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/input/joystick/analog.c b/drivers/input/joystick/analog.c
index 4284080e481d..f871b4f00056 100644
--- a/drivers/input/joystick/analog.c
+++ b/drivers/input/joystick/analog.c
@@ -143,7 +143,7 @@ struct analog_port {
 
 #include <linux/i8253.h>
 
-#define GET_TIME(x)	do { if (cpu_has_tsc) rdtscl(x); else x = get_time_pit(); } while (0)
+#define GET_TIME(x)	do { if (cpu_has_tsc) x = (unsigned int)native_read_tsc(); else x = get_time_pit(); } while (0)
 #define DELTA(x,y)	(cpu_has_tsc ? ((y) - (x)) : ((x) - (y) + ((x) < (y) ? PIT_TICK_RATE / HZ : 0)))
 #define TIME_NAME	(cpu_has_tsc?"TSC":"PIT")
 static unsigned int get_time_pit(void)
@@ -160,7 +160,7 @@ static unsigned int get_time_pit(void)
         return count;
 }
 #elif defined(__x86_64__)
-#define GET_TIME(x)	rdtscl(x)
+#define GET_TIME(x)	do { x = (unsigned int)native_read_tsc(); } while (0)
 #define DELTA(x,y)	((y)-(x))
 #define TIME_NAME	"TSC"
 #elif defined(__alpha__) || defined(CONFIG_MN10300) || defined(CONFIG_ARM) || defined(CONFIG_ARM64) || defined(CONFIG_TILE)
-- 
2.4.2

Re: [PATCH v2 10/17] input/joystick/analog: Switch from rdtscl() to native_read_tsc()

[Dmitry Torokhov]

On Fri, Jun 12, 2015 at 04:44:50PM -0700, Andy Lutomirski wrote:
> This timing code is hideous, and this doesn't help.  It gets rid of
> one of the last users of rdtscl, though.
> 
> Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> Cc: linux-input@vger.kernel.org
> Signed-off-by: Andy Lutomirski <luto@kernel.org>

Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

> ---
>  drivers/input/joystick/analog.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/input/joystick/analog.c b/drivers/input/joystick/analog.c
> index 4284080e481d..f871b4f00056 100644
> --- a/drivers/input/joystick/analog.c
> +++ b/drivers/input/joystick/analog.c
> @@ -143,7 +143,7 @@ struct analog_port {
>  
>  #include <linux/i8253.h>
>  
> -#define GET_TIME(x)	do { if (cpu_has_tsc) rdtscl(x); else x = get_time_pit(); } while (0)
> +#define GET_TIME(x)	do { if (cpu_has_tsc) x = (unsigned int)native_read_tsc(); else x = get_time_pit(); } while (0)
>  #define DELTA(x,y)	(cpu_has_tsc ? ((y) - (x)) : ((x) - (y) + ((x) < (y) ? PIT_TICK_RATE / HZ : 0)))
>  #define TIME_NAME	(cpu_has_tsc?"TSC":"PIT")
>  static unsigned int get_time_pit(void)
> @@ -160,7 +160,7 @@ static unsigned int get_time_pit(void)
>          return count;
>  }
>  #elif defined(__x86_64__)
> -#define GET_TIME(x)	rdtscl(x)
> +#define GET_TIME(x)	do { x = (unsigned int)native_read_tsc(); } while (0)
>  #define DELTA(x,y)	((y)-(x))
>  #define TIME_NAME	"TSC"
>  #elif defined(__alpha__) || defined(CONFIG_MN10300) || defined(CONFIG_ARM) || defined(CONFIG_ARM64) || defined(CONFIG_TILE)
> -- 
> 2.4.2
> 

-- 
Dmitry

Re: [PATCH v2 10/17] input/joystick/analog: Switch from rdtscl() to native_read_tsc()

[Andy Lutomirski]

Is it okay for -tip to take this and the other one you just acked?

Thanks,
Andy

On Tue, Jun 16, 2015 at 4:03 PM, Dmitry Torokhov
<dmitry.torokhov@gmail.com> wrote:
> On Fri, Jun 12, 2015 at 04:44:50PM -0700, Andy Lutomirski wrote:
>> This timing code is hideous, and this doesn't help.  It gets rid of
>> one of the last users of rdtscl, though.
>>
>> Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
>> Cc: linux-input@vger.kernel.org
>> Signed-off-by: Andy Lutomirski <luto@kernel.org>
>
> Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
>
>> ---
>>  drivers/input/joystick/analog.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/input/joystick/analog.c b/drivers/input/joystick/analog.c
>> index 4284080e481d..f871b4f00056 100644
>> --- a/drivers/input/joystick/analog.c
>> +++ b/drivers/input/joystick/analog.c
>> @@ -143,7 +143,7 @@ struct analog_port {
>>
>>  #include <linux/i8253.h>
>>
>> -#define GET_TIME(x)  do { if (cpu_has_tsc) rdtscl(x); else x = get_time_pit(); } while (0)
>> +#define GET_TIME(x)  do { if (cpu_has_tsc) x = (unsigned int)native_read_tsc(); else x = get_time_pit(); } while (0)
>>  #define DELTA(x,y)   (cpu_has_tsc ? ((y) - (x)) : ((x) - (y) + ((x) < (y) ? PIT_TICK_RATE / HZ : 0)))
>>  #define TIME_NAME    (cpu_has_tsc?"TSC":"PIT")
>>  static unsigned int get_time_pit(void)
>> @@ -160,7 +160,7 @@ static unsigned int get_time_pit(void)
>>          return count;
>>  }
>>  #elif defined(__x86_64__)
>> -#define GET_TIME(x)  rdtscl(x)
>> +#define GET_TIME(x)  do { x = (unsigned int)native_read_tsc(); } while (0)
>>  #define DELTA(x,y)   ((y)-(x))
>>  #define TIME_NAME    "TSC"
>>  #elif defined(__alpha__) || defined(CONFIG_MN10300) || defined(CONFIG_ARM) || defined(CONFIG_ARM64) || defined(CONFIG_TILE)
>> --
>> 2.4.2
>>
>
> --
> Dmitry



-- 
Andy Lutomirski
AMA Capital Management, LLC

Re: [PATCH v2 10/17] input/joystick/analog: Switch from rdtscl() to native_read_tsc()

[Dmitry Torokhov]

On June 16, 2015 4:09:06 PM PDT, Andy Lutomirski <luto@amacapital.net> wrote:
>Is it okay for -tip to take this and the other one you just acked?

Yeah, that's fine.


Thanks.

-- 
Dmitry

[PATCH v2 11/17] drivers/input/gameport: Replace rdtscl() with native_read_tsc()

[Andy Lutomirski]

It's unclear to me why this code exists in the first place.

Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: linux-input@vger.kernel.org
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 drivers/input/gameport/gameport.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/input/gameport/gameport.c b/drivers/input/gameport/gameport.c
index e853a2134680..abc0cb22e750 100644
--- a/drivers/input/gameport/gameport.c
+++ b/drivers/input/gameport/gameport.c
@@ -149,9 +149,9 @@ static int old_gameport_measure_speed(struct gameport *gameport)
 
 	for(i = 0; i < 50; i++) {
 		local_irq_save(flags);
-		rdtscl(t1);
+		t1 = native_read_tsc();
 		for (t = 0; t < 50; t++) gameport_read(gameport);
-		rdtscl(t2);
+		t2 = native_read_tsc();
 		local_irq_restore(flags);
 		udelay(i * 10);
 		if (t2 - t1 < tx) tx = t2 - t1;
-- 
2.4.2

Re: [PATCH v2 11/17] drivers/input/gameport: Replace rdtscl() with native_read_tsc()

[Dmitry Torokhov]

On Fri, Jun 12, 2015 at 04:44:51PM -0700, Andy Lutomirski wrote:
> It's unclear to me why this code exists in the first place.
> 
> Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> Cc: linux-input@vger.kernel.org
> Signed-off-by: Andy Lutomirski <luto@kernel.org>

Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

> ---
>  drivers/input/gameport/gameport.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/input/gameport/gameport.c b/drivers/input/gameport/gameport.c
> index e853a2134680..abc0cb22e750 100644
> --- a/drivers/input/gameport/gameport.c
> +++ b/drivers/input/gameport/gameport.c
> @@ -149,9 +149,9 @@ static int old_gameport_measure_speed(struct gameport *gameport)
>  
>  	for(i = 0; i < 50; i++) {
>  		local_irq_save(flags);
> -		rdtscl(t1);
> +		t1 = native_read_tsc();
>  		for (t = 0; t < 50; t++) gameport_read(gameport);
> -		rdtscl(t2);
> +		t2 = native_read_tsc();
>  		local_irq_restore(flags);
>  		udelay(i * 10);
>  		if (t2 - t1 < tx) tx = t2 - t1;
> -- 
> 2.4.2
> 

-- 
Dmitry

[PATCH v2 12/17] x86/tsc: Remove rdtscl()

[Andy Lutomirski]

It has no more callers, and it was never a very sensible interface
to begin with.  Users of the TSC should either read all 64 bits or
explicitly throw out the high bits.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/include/asm/msr.h | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index 626f78199665..c89ed6ceed02 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -189,9 +189,6 @@ do {							\
 
 #endif	/* !CONFIG_PARAVIRT */
 
-#define rdtscl(low)						\
-	((low) = (u32)native_read_tsc())
-
 /*
  * 64-bit version of wrmsr_safe():
  */
-- 
2.4.2

[PATCH v2 13/17] x86/tsc: Rename native_read_tsc() to rdtsc_unordered()

[Andy Lutomirski]

Now that there is no paravirt TSC, the "native" is inappropriate.
The fact that rdtsc is not ordered can catch people by surprise, so
call it rdtsc_unordered().

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/boot/compressed/aslr.c                      |  2 +-
 arch/x86/entry/vdso/vclock_gettime.c                 |  2 +-
 arch/x86/include/asm/msr.h                           | 11 ++++++++++-
 arch/x86/include/asm/pvclock.h                       |  2 +-
 arch/x86/include/asm/stackprotector.h                |  2 +-
 arch/x86/include/asm/tsc.h                           |  2 +-
 arch/x86/kernel/apb_timer.c                          |  8 ++++----
 arch/x86/kernel/apic/apic.c                          |  8 ++++----
 arch/x86/kernel/cpu/amd.c                            |  4 ++--
 arch/x86/kernel/cpu/mcheck/mce.c                     |  4 ++--
 arch/x86/kernel/espfix_64.c                          |  2 +-
 arch/x86/kernel/hpet.c                               |  4 ++--
 arch/x86/kernel/trace_clock.c                        |  2 +-
 arch/x86/kernel/tsc.c                                |  4 ++--
 arch/x86/kvm/lapic.c                                 |  4 ++--
 arch/x86/kvm/svm.c                                   |  4 ++--
 arch/x86/kvm/vmx.c                                   |  4 ++--
 arch/x86/kvm/x86.c                                   | 12 ++++++------
 arch/x86/lib/delay.c                                 |  8 ++++----
 drivers/input/gameport/gameport.c                    |  4 ++--
 drivers/input/joystick/analog.c                      |  4 ++--
 drivers/net/hamradio/baycom_epp.c                    |  2 +-
 drivers/thermal/intel_powerclamp.c                   |  4 ++--
 tools/power/cpupower/debug/kernel/cpufreq-test_tsc.c |  4 ++--
 24 files changed, 58 insertions(+), 49 deletions(-)

diff --git a/arch/x86/boot/compressed/aslr.c b/arch/x86/boot/compressed/aslr.c
index ea33236190b1..487a8a980da3 100644
--- a/arch/x86/boot/compressed/aslr.c
+++ b/arch/x86/boot/compressed/aslr.c
@@ -82,7 +82,7 @@ static unsigned long get_random_long(void)
 
 	if (has_cpuflag(X86_FEATURE_TSC)) {
 		debug_putstr(" RDTSC");
-		raw = native_read_tsc();
+		raw = rdtsc_unordered();
 
 		random ^= raw;
 		use_i8254 = false;
diff --git a/arch/x86/entry/vdso/vclock_gettime.c b/arch/x86/entry/vdso/vclock_gettime.c
index 972b488ac16a..f9a0429875a7 100644
--- a/arch/x86/entry/vdso/vclock_gettime.c
+++ b/arch/x86/entry/vdso/vclock_gettime.c
@@ -186,7 +186,7 @@ notrace static cycle_t vread_tsc(void)
 	 * but no one has ever seen it happen.
 	 */
 	rdtsc_barrier();
-	ret = (cycle_t)native_read_tsc();
+	ret = (cycle_t)rdtsc_unordered();
 
 	last = gtod->cycle_last;
 
diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index c89ed6ceed02..e04f36f65c95 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -109,7 +109,16 @@ notrace static inline int native_write_msr_safe(unsigned int msr,
 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_unordered() - returns the current TSC without ordering constraints
+ *
+ * rdtsc_unordered() 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_unordered(void)
 {
 	DECLARE_ARGS(val, low, high);
 
diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h
index 71bd485c2986..cfd4e89c3acf 100644
--- a/arch/x86/include/asm/pvclock.h
+++ b/arch/x86/include/asm/pvclock.h
@@ -62,7 +62,7 @@ static inline u64 pvclock_scale_delta(u64 delta, u32 mul_frac, int shift)
 static __always_inline
 u64 pvclock_get_nsec_offset(const struct pvclock_vcpu_time_info *src)
 {
-	u64 delta = native_read_tsc() - src->tsc_timestamp;
+	u64 delta = rdtsc_unordered() - src->tsc_timestamp;
 	return pvclock_scale_delta(delta, src->tsc_to_system_mul,
 				   src->tsc_shift);
 }
diff --git a/arch/x86/include/asm/stackprotector.h b/arch/x86/include/asm/stackprotector.h
index bc5fa2af112e..11422aa255e6 100644
--- a/arch/x86/include/asm/stackprotector.h
+++ b/arch/x86/include/asm/stackprotector.h
@@ -72,7 +72,7 @@ static __always_inline void boot_init_stack_canary(void)
 	 * on during the bootup the random pool has true entropy too.
 	 */
 	get_random_bytes(&canary, sizeof(canary));
-	tsc = native_read_tsc();
+	tsc = rdtsc_unordered();
 	canary += tsc + (tsc << 32UL);
 
 	current->stack_canary = canary;
diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h
index b4883902948b..6e10f8b2252e 100644
--- a/arch/x86/include/asm/tsc.h
+++ b/arch/x86/include/asm/tsc.h
@@ -26,7 +26,7 @@ static inline cycles_t get_cycles(void)
 		return 0;
 #endif
 
-	return native_read_tsc();
+	return rdtsc_unordered();
 }
 
 extern void tsc_init(void);
diff --git a/arch/x86/kernel/apb_timer.c b/arch/x86/kernel/apb_timer.c
index 25efa534c4e4..125d96b12141 100644
--- a/arch/x86/kernel/apb_timer.c
+++ b/arch/x86/kernel/apb_timer.c
@@ -263,7 +263,7 @@ static int apbt_clocksource_register(void)
 
 	/* Verify whether apbt counter works */
 	t1 = dw_apb_clocksource_read(clocksource_apbt);
-	start = native_read_tsc();
+	start = rdtsc_unordered();
 
 	/*
 	 * We don't know the TSC frequency yet, but waiting for
@@ -273,7 +273,7 @@ static int apbt_clocksource_register(void)
 	 */
 	do {
 		rep_nop();
-		now = native_read_tsc();
+		now = rdtsc_unordered();
 	} while ((now - start) < 200000UL);
 
 	/* APBT is the only always on clocksource, it has to work! */
@@ -390,13 +390,13 @@ unsigned long apbt_quick_calibrate(void)
 	old = dw_apb_clocksource_read(clocksource_apbt);
 	old += loop;
 
-	t1 = native_read_tsc();
+	t1 = rdtsc_unordered();
 
 	do {
 		new = dw_apb_clocksource_read(clocksource_apbt);
 	} while (new < old);
 
-	t2 = native_read_tsc();
+	t2 = rdtsc_unordered();
 
 	shift = 5;
 	if (unlikely(loop >> shift == 0)) {
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 51af1ed1ae2e..b9a46bf64e24 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -457,7 +457,7 @@ static int lapic_next_deadline(unsigned long delta,
 {
 	u64 tsc;
 
-	tsc = native_read_tsc();
+	tsc = rdtsc_unordered();
 	wrmsrl(MSR_IA32_TSC_DEADLINE, tsc + (((u64) delta) * TSC_DIVISOR));
 	return 0;
 }
@@ -592,7 +592,7 @@ static void __init lapic_cal_handler(struct clock_event_device *dev)
 	unsigned long pm = acpi_pm_read_early();
 
 	if (cpu_has_tsc)
-		tsc = native_read_tsc();
+		tsc = rdtsc_unordered();
 
 	switch (lapic_cal_loops++) {
 	case 0:
@@ -1209,7 +1209,7 @@ void setup_local_APIC(void)
 	long long max_loops = cpu_khz ? cpu_khz : 1000000;
 
 	if (cpu_has_tsc)
-		tsc = native_read_tsc();
+		tsc = rdtsc_unordered();
 
 	if (disable_apic) {
 		disable_ioapic_support();
@@ -1293,7 +1293,7 @@ void setup_local_APIC(void)
 		}
 		if (queued) {
 			if (cpu_has_tsc && cpu_khz) {
-				ntsc = native_read_tsc();
+				ntsc = rdtsc_unordered();
 				max_loops = (cpu_khz << 10) - (ntsc - tsc);
 			} else
 				max_loops--;
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index c5ceec532799..196f2131f44d 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -118,10 +118,10 @@ static void init_amd_k6(struct cpuinfo_x86 *c)
 
 		n = K6_BUG_LOOP;
 		f_vide = vide;
-		d = native_read_tsc();
+		d = rdtsc_unordered();
 		while (n--)
 			f_vide();
-		d2 = native_read_tsc();
+		d2 = rdtsc_unordered();
 		d = d2-d;
 
 		if (d > 20*K6_BUG_LOOP)
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index a5283d2d0094..e2c9311bf098 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -125,7 +125,7 @@ void mce_setup(struct mce *m)
 {
 	memset(m, 0, sizeof(struct mce));
 	m->cpu = m->extcpu = smp_processor_id();
-	m->tsc = native_read_tsc();
+	m->tsc = rdtsc_unordered();
 	/* We hope get_seconds stays lockless */
 	m->time = get_seconds();
 	m->cpuvendor = boot_cpu_data.x86_vendor;
@@ -1784,7 +1784,7 @@ static void collect_tscs(void *data)
 {
 	unsigned long *cpu_tsc = (unsigned long *)data;
 
-	cpu_tsc[smp_processor_id()] = native_read_tsc();
+	cpu_tsc[smp_processor_id()] = rdtsc_unordered();
 }
 
 static int mce_apei_read_done;
diff --git a/arch/x86/kernel/espfix_64.c b/arch/x86/kernel/espfix_64.c
index 334a2a9c034d..e1d2f6839f49 100644
--- a/arch/x86/kernel/espfix_64.c
+++ b/arch/x86/kernel/espfix_64.c
@@ -110,7 +110,7 @@ static void init_espfix_random(void)
 	 */
 	if (!arch_get_random_long(&rand)) {
 		/* The constant is an arbitrary large prime */
-		rand = native_read_tsc();
+		rand = rdtsc_unordered();
 		rand *= 0xc345c6b72fd16123UL;
 	}
 
diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index ccf677cd9adc..141bba987f9b 100644
--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -734,7 +734,7 @@ static int hpet_clocksource_register(void)
 
 	/* Verify whether hpet counter works */
 	t1 = hpet_readl(HPET_COUNTER);
-	start = native_read_tsc();
+	start = rdtsc_unordered();
 
 	/*
 	 * We don't know the TSC frequency yet, but waiting for
@@ -744,7 +744,7 @@ static int hpet_clocksource_register(void)
 	 */
 	do {
 		rep_nop();
-		now = native_read_tsc();
+		now = rdtsc_unordered();
 	} while ((now - start) < 200000UL);
 
 	if (t1 == hpet_readl(HPET_COUNTER)) {
diff --git a/arch/x86/kernel/trace_clock.c b/arch/x86/kernel/trace_clock.c
index bd8f4d41bd56..c0ab0bed02ae 100644
--- a/arch/x86/kernel/trace_clock.c
+++ b/arch/x86/kernel/trace_clock.c
@@ -15,7 +15,7 @@ u64 notrace trace_clock_x86_tsc(void)
 	u64 ret;
 
 	rdtsc_barrier();
-	ret = native_read_tsc();
+	ret = rdtsc_unordered();
 
 	return ret;
 }
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index e66f5dcaeb63..5eb4d91ce9db 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -248,7 +248,7 @@ static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
 
 	data = cyc2ns_write_begin(cpu);
 
-	tsc_now = native_read_tsc();
+	tsc_now = rdtsc_unordered();
 	ns_now = cycles_2_ns(tsc_now);
 
 	/*
@@ -290,7 +290,7 @@ u64 native_sched_clock(void)
 	}
 
 	/* read the Time Stamp Counter: */
-	tsc_now = native_read_tsc();
+	tsc_now = rdtsc_unordered();
 
 	/* return the value in ns */
 	return cycles_2_ns(tsc_now);
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 629af0f1c5c4..5b13eeea578a 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1148,7 +1148,7 @@ void wait_lapic_expire(struct kvm_vcpu *vcpu)
 
 	tsc_deadline = apic->lapic_timer.expired_tscdeadline;
 	apic->lapic_timer.expired_tscdeadline = 0;
-	guest_tsc = kvm_x86_ops->read_l1_tsc(vcpu, native_read_tsc());
+	guest_tsc = kvm_x86_ops->read_l1_tsc(vcpu, rdtsc_unordered());
 	trace_kvm_wait_lapic_expire(vcpu->vcpu_id, guest_tsc - tsc_deadline);
 
 	/* __delay is delay_tsc whenever the hardware has TSC, thus always.  */
@@ -1216,7 +1216,7 @@ static void start_apic_timer(struct kvm_lapic *apic)
 		local_irq_save(flags);
 
 		now = apic->lapic_timer.timer.base->get_time();
-		guest_tsc = kvm_x86_ops->read_l1_tsc(vcpu, native_read_tsc());
+		guest_tsc = kvm_x86_ops->read_l1_tsc(vcpu, rdtsc_unordered());
 		if (likely(tscdeadline > guest_tsc)) {
 			ns = (tscdeadline - guest_tsc) * 1000000ULL;
 			do_div(ns, this_tsc_khz);
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 9afa233b5482..ec26eb38a768 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1077,7 +1077,7 @@ static u64 svm_compute_tsc_offset(struct kvm_vcpu *vcpu, u64 target_tsc)
 {
 	u64 tsc;
 
-	tsc = svm_scale_tsc(vcpu, native_read_tsc());
+	tsc = svm_scale_tsc(vcpu, rdtsc_unordered());
 
 	return target_tsc - tsc;
 }
@@ -3074,7 +3074,7 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, unsigned ecx, u64 *data)
 	switch (ecx) {
 	case MSR_IA32_TSC: {
 		*data = svm->vmcb->control.tsc_offset +
-			svm_scale_tsc(vcpu, native_read_tsc());
+			svm_scale_tsc(vcpu, rdtsc_unordered());
 
 		break;
 	}
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index fcff42100948..b220331bc575 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2236,7 +2236,7 @@ static u64 guest_read_tsc(void)
 {
 	u64 host_tsc, tsc_offset;
 
-	host_tsc = native_read_tsc();
+	host_tsc = rdtsc_unordered();
 	tsc_offset = vmcs_read64(TSC_OFFSET);
 	return host_tsc + tsc_offset;
 }
@@ -2317,7 +2317,7 @@ static void vmx_adjust_tsc_offset(struct kvm_vcpu *vcpu, s64 adjustment, bool ho
 
 static u64 vmx_compute_tsc_offset(struct kvm_vcpu *vcpu, u64 target_tsc)
 {
-	return target_tsc - native_read_tsc();
+	return target_tsc - rdtsc_unordered();
 }
 
 static bool guest_cpuid_has_vmx(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c26faf408bce..a9a3f31311e1 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1430,7 +1430,7 @@ static cycle_t read_tsc(void)
 	 * but no one has ever seen it happen.
 	 */
 	rdtsc_barrier();
-	ret = (cycle_t)native_read_tsc();
+	ret = (cycle_t)rdtsc_unordered();
 
 	last = pvclock_gtod_data.clock.cycle_last;
 
@@ -1621,7 +1621,7 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
 		return 1;
 	}
 	if (!use_master_clock) {
-		host_tsc = native_read_tsc();
+		host_tsc = rdtsc_unordered();
 		kernel_ns = get_kernel_ns();
 	}
 
@@ -2945,7 +2945,7 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 
 	if (unlikely(vcpu->cpu != cpu) || check_tsc_unstable()) {
 		s64 tsc_delta = !vcpu->arch.last_host_tsc ? 0 :
-				native_read_tsc() - vcpu->arch.last_host_tsc;
+				rdtsc_unordered() - vcpu->arch.last_host_tsc;
 		if (tsc_delta < 0)
 			mark_tsc_unstable("KVM discovered backwards TSC");
 		if (check_tsc_unstable()) {
@@ -2973,7 +2973,7 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 {
 	kvm_x86_ops->vcpu_put(vcpu);
 	kvm_put_guest_fpu(vcpu);
-	vcpu->arch.last_host_tsc = native_read_tsc();
+	vcpu->arch.last_host_tsc = rdtsc_unordered();
 }
 
 static int kvm_vcpu_ioctl_get_lapic(struct kvm_vcpu *vcpu,
@@ -6388,7 +6388,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 		hw_breakpoint_restore();
 
 	vcpu->arch.last_guest_tsc = kvm_x86_ops->read_l1_tsc(vcpu,
-							   native_read_tsc());
+							   rdtsc_unordered());
 
 	vcpu->mode = OUTSIDE_GUEST_MODE;
 	smp_wmb();
@@ -7186,7 +7186,7 @@ int kvm_arch_hardware_enable(void)
 	if (ret != 0)
 		return ret;
 
-	local_tsc = native_read_tsc();
+	local_tsc = rdtsc_unordered();
 	stable = !check_tsc_unstable();
 	list_for_each_entry(kvm, &vm_list, vm_list) {
 		kvm_for_each_vcpu(i, vcpu, kvm) {
diff --git a/arch/x86/lib/delay.c b/arch/x86/lib/delay.c
index 35115f3786a9..a524708fa165 100644
--- a/arch/x86/lib/delay.c
+++ b/arch/x86/lib/delay.c
@@ -55,10 +55,10 @@ static void delay_tsc(unsigned long __loops)
 	preempt_disable();
 	cpu = smp_processor_id();
 	rdtsc_barrier();
-	bclock = native_read_tsc();
+	bclock = rdtsc_unordered();
 	for (;;) {
 		rdtsc_barrier();
-		now = native_read_tsc();
+		now = rdtsc_unordered();
 		if ((now - bclock) >= loops)
 			break;
 
@@ -80,7 +80,7 @@ static void delay_tsc(unsigned long __loops)
 			loops -= (now - bclock);
 			cpu = smp_processor_id();
 			rdtsc_barrier();
-			bclock = native_read_tsc();
+			bclock = rdtsc_unordered();
 		}
 	}
 	preempt_enable();
@@ -100,7 +100,7 @@ void use_tsc_delay(void)
 int read_current_timer(unsigned long *timer_val)
 {
 	if (delay_fn == delay_tsc) {
-		*timer_val = native_read_tsc();
+		*timer_val = rdtsc_unordered();
 		return 0;
 	}
 	return -1;
diff --git a/drivers/input/gameport/gameport.c b/drivers/input/gameport/gameport.c
index abc0cb22e750..5671c3e35fb6 100644
--- a/drivers/input/gameport/gameport.c
+++ b/drivers/input/gameport/gameport.c
@@ -149,9 +149,9 @@ static int old_gameport_measure_speed(struct gameport *gameport)
 
 	for(i = 0; i < 50; i++) {
 		local_irq_save(flags);
-		t1 = native_read_tsc();
+		t1 = rdtsc_unordered();
 		for (t = 0; t < 50; t++) gameport_read(gameport);
-		t2 = native_read_tsc();
+		t2 = rdtsc_unordered();
 		local_irq_restore(flags);
 		udelay(i * 10);
 		if (t2 - t1 < tx) tx = t2 - t1;
diff --git a/drivers/input/joystick/analog.c b/drivers/input/joystick/analog.c
index f871b4f00056..3b251daa2092 100644
--- a/drivers/input/joystick/analog.c
+++ b/drivers/input/joystick/analog.c
@@ -143,7 +143,7 @@ struct analog_port {
 
 #include <linux/i8253.h>
 
-#define GET_TIME(x)	do { if (cpu_has_tsc) x = (unsigned int)native_read_tsc(); else x = get_time_pit(); } while (0)
+#define GET_TIME(x)	do { if (cpu_has_tsc) x = (unsigned int)rdtsc_unordered(); else x = get_time_pit(); } while (0)
 #define DELTA(x,y)	(cpu_has_tsc ? ((y) - (x)) : ((x) - (y) + ((x) < (y) ? PIT_TICK_RATE / HZ : 0)))
 #define TIME_NAME	(cpu_has_tsc?"TSC":"PIT")
 static unsigned int get_time_pit(void)
@@ -160,7 +160,7 @@ static unsigned int get_time_pit(void)
         return count;
 }
 #elif defined(__x86_64__)
-#define GET_TIME(x)	do { x = (unsigned int)native_read_tsc(); } while (0)
+#define GET_TIME(x)	do { x = (unsigned int)rdtsc_unordered(); } while (0)
 #define DELTA(x,y)	((y)-(x))
 #define TIME_NAME	"TSC"
 #elif defined(__alpha__) || defined(CONFIG_MN10300) || defined(CONFIG_ARM) || defined(CONFIG_ARM64) || defined(CONFIG_TILE)
diff --git a/drivers/net/hamradio/baycom_epp.c b/drivers/net/hamradio/baycom_epp.c
index 44e5c3b5e0af..8302a54bb583 100644
--- a/drivers/net/hamradio/baycom_epp.c
+++ b/drivers/net/hamradio/baycom_epp.c
@@ -638,7 +638,7 @@ static int receive(struct net_device *dev, int cnt)
 #define GETTICK(x)                                                \
 ({                                                                \
 	if (cpu_has_tsc)                                          \
-		x = (unsigned int)native_read_tsc();		  \
+		x = (unsigned int)rdtsc_unordered();		  \
 })
 #else /* __i386__ */
 #define GETTICK(x)
diff --git a/drivers/thermal/intel_powerclamp.c b/drivers/thermal/intel_powerclamp.c
index 933c5e599d1d..ea6fd07739fd 100644
--- a/drivers/thermal/intel_powerclamp.c
+++ b/drivers/thermal/intel_powerclamp.c
@@ -340,7 +340,7 @@ static bool powerclamp_adjust_controls(unsigned int target_ratio,
 
 	/* check result for the last window */
 	msr_now = pkg_state_counter();
-	tsc_now = native_read_tsc();
+	tsc_now = rdtsc_unordered();
 
 	/* calculate pkg cstate vs tsc ratio */
 	if (!msr_last || !tsc_last)
@@ -482,7 +482,7 @@ static void poll_pkg_cstate(struct work_struct *dummy)
 	u64 val64;
 
 	msr_now = pkg_state_counter();
-	tsc_now = native_read_tsc();
+	tsc_now = rdtsc_unordered();
 	jiffies_now = jiffies;
 
 	/* calculate pkg cstate vs tsc ratio */
diff --git a/tools/power/cpupower/debug/kernel/cpufreq-test_tsc.c b/tools/power/cpupower/debug/kernel/cpufreq-test_tsc.c
index f02b0c0bff9b..511b7cb3a9c8 100644
--- a/tools/power/cpupower/debug/kernel/cpufreq-test_tsc.c
+++ b/tools/power/cpupower/debug/kernel/cpufreq-test_tsc.c
@@ -81,11 +81,11 @@ static int __init cpufreq_test_tsc(void)
 
 	printk(KERN_DEBUG "start--> \n");
 	then = read_pmtmr();
-	then_tsc = native_read_tsc();
+	then_tsc = rdtsc_unordered();
 	for (i=0;i<20;i++) {
 		mdelay(100);
 		now = read_pmtmr();
-		now_tsc = native_read_tsc();
+		now_tsc = rdtsc_unordered();
 		diff = (now - then) & 0xFFFFFF;
 		diff_tsc = now_tsc - then_tsc;
 		printk(KERN_DEBUG "t1: %08u t2: %08u diff_pmtmr: %08u diff_tsc: %016llu\n", then, now, diff, diff_tsc);
-- 
2.4.2

Re: [PATCH v2 13/17] x86/tsc: Rename native_read_tsc() to rdtsc_unordered()

[Borislav Petkov]

On Fri, Jun 12, 2015 at 04:44:53PM -0700, Andy Lutomirski wrote:
> Now that there is no paravirt TSC, the "native" is inappropriate.
> The fact that rdtsc is not ordered can catch people by surprise, so
> call it rdtsc_unordered().
> 
> Signed-off-by: Andy Lutomirski <luto@kernel.org>

...

> @@ -109,7 +109,16 @@ notrace static inline int native_write_msr_safe(unsigned int msr,
>  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_unordered() - returns the current TSC without ordering constraints
> + *
> + * rdtsc_unordered() 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_unordered(void)

I like the rdtsc_ordered() thing because it wraps the barrier and people
cannot just forget it. But let's call this not rdtsc_unordered() but
simply

	rdtsc()

The "_unordered" suffix is unnecessary IMO since this function is a
simple wrapper around the hw insn and we do that naming scheme with all
such wrappers.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
--

Re: [PATCH v2 13/17] x86/tsc: Rename native_read_tsc() to rdtsc_unordered()

[Andy Lutomirski]

On Sat, Jun 13, 2015 at 1:57 AM, Borislav Petkov <bp@suse.de> wrote:
> On Fri, Jun 12, 2015 at 04:44:53PM -0700, Andy Lutomirski wrote:
>> Now that there is no paravirt TSC, the "native" is inappropriate.
>> The fact that rdtsc is not ordered can catch people by surprise, so
>> call it rdtsc_unordered().
>>
>> Signed-off-by: Andy Lutomirski <luto@kernel.org>
>
> ...
>
>> @@ -109,7 +109,16 @@ notrace static inline int native_write_msr_safe(unsigned int msr,
>>  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_unordered() - returns the current TSC without ordering constraints
>> + *
>> + * rdtsc_unordered() 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_unordered(void)
>
> I like the rdtsc_ordered() thing because it wraps the barrier and people
> cannot just forget it. But let's call this not rdtsc_unordered() but
> simply
>
>         rdtsc()
>
> The "_unordered" suffix is unnecessary IMO since this function is a
> simple wrapper around the hw insn and we do that naming scheme with all
> such wrappers.

I could go either way here.  rdtsc() is weird because people seem to
forget about the barrier.  Maybe I'm being unnecessarily paranoid.

--Andy

>
> --
> Regards/Gruss,
>     Boris.
>
> ECO tip #101: Trim your mails when you reply.
> --



-- 
Andy Lutomirski
AMA Capital Management, LLC

Re: [PATCH v2 13/17] x86/tsc: Rename native_read_tsc() to rdtsc_unordered()

[Borislav Petkov]

On Sat, Jun 13, 2015 at 11:25:49AM -0700, Andy Lutomirski wrote:
> I could go either way here.  rdtsc() is weird because people seem to
> forget about the barrier.

Yeah, our job is only to give them enough rope...

> Maybe I'm being unnecessarily paranoid.

You can always slap a comment above the rdtsc() definition saying that
people should use the _ordered() version if they wanna order. :)

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
--

[PATCH v2 14/17] x86/tsc: Move rdtsc_barrier() and rename it to barrier_before_rdtsc()

[Andy Lutomirski]

rdtsc_barrier() (i.e. MFENCE or LFENCE depending on vendor) is
supported by the docs as a barrier immediately before RDTSC.  There
is neither empirical evidence that it's needed at all after RDTSC
nor is there any reason to believe that the type of fence to put
after RDTSC (if any) would be the same as a fence before RDTSC.

Rename the function accordingly.  While we're at it, move it so it
lives with the rest of the RDTSC inlines.

There are some callers that look odd now.  That's fine -- they are
odd.  A subsequent patch will fix them up.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/entry/vdso/vclock_gettime.c |  2 +-
 arch/x86/include/asm/barrier.h       | 11 -----------
 arch/x86/include/asm/msr.h           | 21 +++++++++++++++++++++
 arch/x86/include/asm/pvclock.h       |  6 +++---
 arch/x86/kernel/trace_clock.c        |  2 +-
 arch/x86/kernel/tsc_sync.c           |  8 ++++----
 arch/x86/kvm/x86.c                   |  2 +-
 arch/x86/lib/delay.c                 |  6 +++---
 arch/x86/um/asm/barrier.h            |  4 +---
 9 files changed, 35 insertions(+), 27 deletions(-)

diff --git a/arch/x86/entry/vdso/vclock_gettime.c b/arch/x86/entry/vdso/vclock_gettime.c
index f9a0429875a7..0f91cc7373df 100644
--- a/arch/x86/entry/vdso/vclock_gettime.c
+++ b/arch/x86/entry/vdso/vclock_gettime.c
@@ -185,7 +185,7 @@ notrace static cycle_t vread_tsc(void)
 	 * as to whether rdtsc can be reordered with later loads,
 	 * but no one has ever seen it happen.
 	 */
-	rdtsc_barrier();
+	barrier_before_rdtsc();
 	ret = (cycle_t)rdtsc_unordered();
 
 	last = gtod->cycle_last;
diff --git a/arch/x86/include/asm/barrier.h b/arch/x86/include/asm/barrier.h
index e51a8f803f55..818cb8788225 100644
--- a/arch/x86/include/asm/barrier.h
+++ b/arch/x86/include/asm/barrier.h
@@ -91,15 +91,4 @@ do {									\
 #define smp_mb__before_atomic()	barrier()
 #define smp_mb__after_atomic()	barrier()
 
-/*
- * Stop RDTSC speculation. This is needed when you need to use RDTSC
- * (or get_cycles or vread that possibly accesses the TSC) in a defined
- * code region.
- */
-static __always_inline void rdtsc_barrier(void)
-{
-	alternative_2("", "mfence", X86_FEATURE_MFENCE_RDTSC,
-			  "lfence", X86_FEATURE_LFENCE_RDTSC);
-}
-
 #endif /* _ASM_X86_BARRIER_H */
diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index e04f36f65c95..a47fb11af5f5 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -127,6 +127,27 @@ static __always_inline unsigned long long rdtsc_unordered(void)
 	return EAX_EDX_VAL(val, low, high);
 }
 
+/**
+ * barrier_before_rdtsc() - memory barrier before rdtsc_unordered
+ *
+ * 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.
+ *
+ * For applications that require monotonicity across multiple CPUs or
+ * that need RDTSC to time code in a defined region, this barrier can be
+ * used before rdtsc_unordered().
+ */
+static __always_inline void barrier_before_rdtsc(void)
+{
+	alternative_2("", "mfence", X86_FEATURE_MFENCE_RDTSC,
+			  "lfence", X86_FEATURE_LFENCE_RDTSC);
+}
+
 static inline unsigned long long native_read_pmc(int counter)
 {
 	DECLARE_ARGS(val, low, high);
diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h
index cfd4e89c3acf..4216986b5535 100644
--- a/arch/x86/include/asm/pvclock.h
+++ b/arch/x86/include/asm/pvclock.h
@@ -79,14 +79,14 @@ unsigned __pvclock_read_cycles(const struct pvclock_vcpu_time_info *src,
 	/* Note: emulated platforms which do not advertise SSE2 support
 	 * result in kvmclock not using the necessary RDTSC barriers.
 	 * Without barriers, it is possible that RDTSC instruction reads from
-	 * the time stamp counter outside rdtsc_barrier protected section
+	 * the time stamp counter outside barrier_before_rdtsc protected section
 	 * below, resulting in violation of monotonicity.
 	 */
-	rdtsc_barrier();
+	barrier_before_rdtsc();
 	offset = pvclock_get_nsec_offset(src);
 	ret = src->system_time + offset;
 	ret_flags = src->flags;
-	rdtsc_barrier();
+	barrier_before_rdtsc();
 
 	*cycles = ret;
 	*flags = ret_flags;
diff --git a/arch/x86/kernel/trace_clock.c b/arch/x86/kernel/trace_clock.c
index c0ab0bed02ae..60ddc0501beb 100644
--- a/arch/x86/kernel/trace_clock.c
+++ b/arch/x86/kernel/trace_clock.c
@@ -14,7 +14,7 @@ u64 notrace trace_clock_x86_tsc(void)
 {
 	u64 ret;
 
-	rdtsc_barrier();
+	barrier_before_rdtsc();
 	ret = rdtsc_unordered();
 
 	return ret;
diff --git a/arch/x86/kernel/tsc_sync.c b/arch/x86/kernel/tsc_sync.c
index dd8d0791dfb5..cf36e9befb39 100644
--- a/arch/x86/kernel/tsc_sync.c
+++ b/arch/x86/kernel/tsc_sync.c
@@ -46,9 +46,9 @@ static void check_tsc_warp(unsigned int timeout)
 	cycles_t start, now, prev, end;
 	int i;
 
-	rdtsc_barrier();
+	barrier_before_rdtsc();
 	start = get_cycles();
-	rdtsc_barrier();
+	barrier_before_rdtsc();
 	/*
 	 * The measurement runs for 'timeout' msecs:
 	 */
@@ -63,9 +63,9 @@ static void check_tsc_warp(unsigned int timeout)
 		 */
 		arch_spin_lock(&sync_lock);
 		prev = last_tsc;
-		rdtsc_barrier();
+		barrier_before_rdtsc();
 		now = get_cycles();
-		rdtsc_barrier();
+		barrier_before_rdtsc();
 		last_tsc = now;
 		arch_spin_unlock(&sync_lock);
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a9a3f31311e1..dbd2e5b4346a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1429,7 +1429,7 @@ static cycle_t read_tsc(void)
 	 * as to whether rdtsc can be reordered with later loads,
 	 * but no one has ever seen it happen.
 	 */
-	rdtsc_barrier();
+	barrier_before_rdtsc();
 	ret = (cycle_t)rdtsc_unordered();
 
 	last = pvclock_gtod_data.clock.cycle_last;
diff --git a/arch/x86/lib/delay.c b/arch/x86/lib/delay.c
index a524708fa165..d49b98a192ae 100644
--- a/arch/x86/lib/delay.c
+++ b/arch/x86/lib/delay.c
@@ -54,10 +54,10 @@ static void delay_tsc(unsigned long __loops)
 
 	preempt_disable();
 	cpu = smp_processor_id();
-	rdtsc_barrier();
+	barrier_before_rdtsc();
 	bclock = rdtsc_unordered();
 	for (;;) {
-		rdtsc_barrier();
+		barrier_before_rdtsc();
 		now = rdtsc_unordered();
 		if ((now - bclock) >= loops)
 			break;
@@ -79,7 +79,7 @@ static void delay_tsc(unsigned long __loops)
 		if (unlikely(cpu != smp_processor_id())) {
 			loops -= (now - bclock);
 			cpu = smp_processor_id();
-			rdtsc_barrier();
+			barrier_before_rdtsc();
 			bclock = rdtsc_unordered();
 		}
 	}
diff --git a/arch/x86/um/asm/barrier.h b/arch/x86/um/asm/barrier.h
index b9531d343134..f168d818d551 100644
--- a/arch/x86/um/asm/barrier.h
+++ b/arch/x86/um/asm/barrier.h
@@ -49,10 +49,8 @@
  * Stop RDTSC speculation. This is needed when you need to use RDTSC
  * (or get_cycles or vread that possibly accesses the TSC) in a defined
  * code region.
- *
- * (Could use an alternative three way for this if there was one.)
  */
-static inline void rdtsc_barrier(void)
+static inline void barrier_before_rdtsc(void)
 {
 	alternative_2("", "mfence", X86_FEATURE_MFENCE_RDTSC,
 			  "lfence", X86_FEATURE_LFENCE_RDTSC);
-- 
2.4.2

[PATCH v2 15/17] x86: Add rdtsc_ordered() and use it in trivial call sites

[Andy Lutomirski]

barrier_before_rdtsc(); rdtsc_unordered() is an unnecessary mouthful and
requires more thought than should be necessary.  Add an rdtsc_ordered()
helper and replace the trivial call sites with it.

This should not change generated code.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/entry/vdso/vclock_gettime.c | 16 ++--------------
 arch/x86/include/asm/msr.h           | 14 ++++++++++++++
 arch/x86/kernel/trace_clock.c        |  7 +------
 arch/x86/kvm/x86.c                   | 16 ++--------------
 arch/x86/lib/delay.c                 |  9 +++------
 5 files changed, 22 insertions(+), 40 deletions(-)

diff --git a/arch/x86/entry/vdso/vclock_gettime.c b/arch/x86/entry/vdso/vclock_gettime.c
index 0f91cc7373df..ca94fa649251 100644
--- a/arch/x86/entry/vdso/vclock_gettime.c
+++ b/arch/x86/entry/vdso/vclock_gettime.c
@@ -175,20 +175,8 @@ static notrace cycle_t vread_pvclock(int *mode)
 
 notrace static cycle_t vread_tsc(void)
 {
-	cycle_t ret;
-	u64 last;
-
-	/*
-	 * Empirically, a fence (of type that depends on the CPU)
-	 * before rdtsc is enough to ensure that rdtsc is ordered
-	 * with respect to loads.  The various CPU manuals are unclear
-	 * as to whether rdtsc can be reordered with later loads,
-	 * but no one has ever seen it happen.
-	 */
-	barrier_before_rdtsc();
-	ret = (cycle_t)rdtsc_unordered();
-
-	last = gtod->cycle_last;
+	cycle_t ret = (cycle_t)rdtsc_ordered();
+	u64 last = gtod->cycle_last;
 
 	if (likely(ret >= last))
 		return ret;
diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index a47fb11af5f5..22d69d2d1f0d 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -148,6 +148,20 @@ static __always_inline void barrier_before_rdtsc(void)
 			  "lfence", X86_FEATURE_LFENCE_RDTSC);
 }
 
+/**
+ * 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)
+{
+	barrier_before_rdtsc();
+	return rdtsc_unordered();
+}
+
 static inline unsigned long long native_read_pmc(int counter)
 {
 	DECLARE_ARGS(val, low, high);
diff --git a/arch/x86/kernel/trace_clock.c b/arch/x86/kernel/trace_clock.c
index 60ddc0501beb..80bb24d9b880 100644
--- a/arch/x86/kernel/trace_clock.c
+++ b/arch/x86/kernel/trace_clock.c
@@ -12,10 +12,5 @@
  */
 u64 notrace trace_clock_x86_tsc(void)
 {
-	u64 ret;
-
-	barrier_before_rdtsc();
-	ret = rdtsc_unordered();
-
-	return ret;
+	return rdtsc_ordered();
 }
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index dbd2e5b4346a..ba69c06d8150 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1419,20 +1419,8 @@ EXPORT_SYMBOL_GPL(kvm_write_tsc);
 
 static cycle_t read_tsc(void)
 {
-	cycle_t ret;
-	u64 last;
-
-	/*
-	 * Empirically, a fence (of type that depends on the CPU)
-	 * before rdtsc is enough to ensure that rdtsc is ordered
-	 * with respect to loads.  The various CPU manuals are unclear
-	 * as to whether rdtsc can be reordered with later loads,
-	 * but no one has ever seen it happen.
-	 */
-	barrier_before_rdtsc();
-	ret = (cycle_t)rdtsc_unordered();
-
-	last = pvclock_gtod_data.clock.cycle_last;
+	cycle_t ret = (cycle_t)rdtsc_ordered();
+	u64 last = pvclock_gtod_data.clock.cycle_last;
 
 	if (likely(ret >= last))
 		return ret;
diff --git a/arch/x86/lib/delay.c b/arch/x86/lib/delay.c
index d49b98a192ae..82bd6aaafe72 100644
--- a/arch/x86/lib/delay.c
+++ b/arch/x86/lib/delay.c
@@ -54,11 +54,9 @@ static void delay_tsc(unsigned long __loops)
 
 	preempt_disable();
 	cpu = smp_processor_id();
-	barrier_before_rdtsc();
-	bclock = rdtsc_unordered();
+	bclock = rdtsc_ordered();
 	for (;;) {
-		barrier_before_rdtsc();
-		now = rdtsc_unordered();
+		now = rdtsc_ordered();
 		if ((now - bclock) >= loops)
 			break;
 
@@ -79,8 +77,7 @@ static void delay_tsc(unsigned long __loops)
 		if (unlikely(cpu != smp_processor_id())) {
 			loops -= (now - bclock);
 			cpu = smp_processor_id();
-			barrier_before_rdtsc();
-			bclock = rdtsc_unordered();
+			bclock = rdtsc_ordered();
 		}
 	}
 	preempt_enable();
-- 
2.4.2

Re: [PATCH v2 15/17] x86: Add rdtsc_ordered() and use it in trivial call sites

[Borislav Petkov]

On Fri, Jun 12, 2015 at 04:44:55PM -0700, Andy Lutomirski wrote:
> barrier_before_rdtsc(); rdtsc_unordered() is an unnecessary mouthful and
> requires more thought than should be necessary.  Add an rdtsc_ordered()
> helper and replace the trivial call sites with it.
> 
> This should not change generated code.
> 
> Signed-off-by: Andy Lutomirski <luto@kernel.org>
> ---

...

> diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
> index a47fb11af5f5..22d69d2d1f0d 100644
> --- a/arch/x86/include/asm/msr.h
> +++ b/arch/x86/include/asm/msr.h
> @@ -148,6 +148,20 @@ static __always_inline void barrier_before_rdtsc(void)
>  			  "lfence", X86_FEATURE_LFENCE_RDTSC);
>  }
>  
> +/**
> + * 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)
> +{
> +	barrier_before_rdtsc();
> +	return rdtsc_unordered();
> +}
> +

I don't see the final tree state with all those applied (too lazy to
apply them) but why not simply kill barrier_before_rdtsc() and inline
the alternative into rdtsc_ordered()?

I mean, I don't see usage for it somewhere else...

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
--

Re: [PATCH v2 15/17] x86: Add rdtsc_ordered() and use it in trivial call sites

[Andy Lutomirski]

On Sat, Jun 13, 2015 at 2:02 AM, Borislav Petkov <bp@suse.de> wrote:
> On Fri, Jun 12, 2015 at 04:44:55PM -0700, Andy Lutomirski wrote:
>> barrier_before_rdtsc(); rdtsc_unordered() is an unnecessary mouthful and
>> requires more thought than should be necessary.  Add an rdtsc_ordered()
>> helper and replace the trivial call sites with it.
>>
>> This should not change generated code.
>>
>> Signed-off-by: Andy Lutomirski <luto@kernel.org>
>> ---
>
> ...
>
>> diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
>> index a47fb11af5f5..22d69d2d1f0d 100644
>> --- a/arch/x86/include/asm/msr.h
>> +++ b/arch/x86/include/asm/msr.h
>> @@ -148,6 +148,20 @@ static __always_inline void barrier_before_rdtsc(void)
>>                         "lfence", X86_FEATURE_LFENCE_RDTSC);
>>  }
>>
>> +/**
>> + * 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)
>> +{
>> +     barrier_before_rdtsc();
>> +     return rdtsc_unordered();
>> +}
>> +
>
> I don't see the final tree state with all those applied (too lazy to
> apply them) but why not simply kill barrier_before_rdtsc() and inline
> the alternative into rdtsc_ordered()?
>
> I mean, I don't see usage for it somewhere else...

There's the awful, awful code in kvmclock.  I'll fix that as part of
v3 and get rid of barrier_before_rdtsc().

--Andy

[PATCH v2 16/17] x86/tsc: Use rdtsc_ordered() in check_tsc_warp() and drop extra barriers

[Andy Lutomirski]

Using get_cycles was unnecessary: check_tsc_warp() is not called on
TSC-less systems.  Replace barrier_before_rdtsc(); get_cycles() with
rdtsc_ordered().

While we're at it, make the somewhat more dangerous change of
removing barrier_before_rdtsc after RDTSC in the TSC warp check
code.  This should be okay, though -- the vDSO TSC code doesn't have
that barrier, so, if removing the barrier from the warp check would
cause us to detect a warp that we otherwise wouldn't detect, then we
have a genuine bug.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/kernel/tsc_sync.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/tsc_sync.c b/arch/x86/kernel/tsc_sync.c
index cf36e9befb39..78083bf23ed1 100644
--- a/arch/x86/kernel/tsc_sync.c
+++ b/arch/x86/kernel/tsc_sync.c
@@ -39,16 +39,15 @@ static cycles_t max_warp;
 static int nr_warps;
 
 /*
- * TSC-warp measurement loop running on both CPUs:
+ * TSC-warp measurement loop running on both CPUs.  This is not called
+ * if there is no TSC.
  */
 static void check_tsc_warp(unsigned int timeout)
 {
 	cycles_t start, now, prev, end;
 	int i;
 
-	barrier_before_rdtsc();
-	start = get_cycles();
-	barrier_before_rdtsc();
+	start = rdtsc_ordered();
 	/*
 	 * The measurement runs for 'timeout' msecs:
 	 */
@@ -63,9 +62,7 @@ static void check_tsc_warp(unsigned int timeout)
 		 */
 		arch_spin_lock(&sync_lock);
 		prev = last_tsc;
-		barrier_before_rdtsc();
-		now = get_cycles();
-		barrier_before_rdtsc();
+		now = rdtsc_ordered();
 		last_tsc = now;
 		arch_spin_unlock(&sync_lock);
 
@@ -126,7 +123,7 @@ void check_tsc_sync_source(int cpu)
 
 	/*
 	 * No need to check if we already know that the TSC is not
-	 * synchronized:
+	 * synchronized or if we have no TSC.
 	 */
 	if (unsynchronized_tsc())
 		return;
@@ -190,6 +187,7 @@ void check_tsc_sync_target(void)
 {
 	int cpus = 2;
 
+	/* Also aborts if there is no TSC. */
 	if (unsynchronized_tsc() || tsc_clocksource_reliable)
 		return;
 
-- 
2.4.2

[PATCH v2 17/17] x86/tsc: In read_tsc, use rdtsc_ordered() instead of get_cycles()

[Andy Lutomirski]

There are two logical changes here.  First, this removes a check for
cpu_has_tsc.  That check is unnecessary, as we don't register the
TSC as a clocksource on systems that have no TSC.  Second, it adds a
barrier, thus preventing observable non-monotonicity.

I suspect that the missing barrier was never a problem in practice
because system calls themselves were heavy enough barriers to
prevent user code from observing time warps due to speculation.
(Without the corresponding barrier in the vDSO, however,
non-monotonicity is easy to detect.)

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/kernel/tsc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 5eb4d91ce9db..c3b6c04c5bf7 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -961,7 +961,7 @@ static struct clocksource clocksource_tsc;
  */
 static cycle_t read_tsc(struct clocksource *cs)
 {
-	return (cycle_t)get_cycles();
+	return (cycle_t)rdtsc_ordered();
 }
 
 /*
-- 
2.4.2