diff mbox

V5 [PATCH 2/2] x86: Add a LD_PRELOAD IFUNC resolver test for CPU_FEATURE_USABLE

Message ID CAMe9rOo4v_Yx5zxvKGAC+hDEvcXEMnpunEpZAj+3_RGG69mZ2g@mail.gmail.com
State New, archived
Headers show

Commit Message

H.J. Lu Oct. 24, 2018, 12:38 p.m. UTC
On 10/24/18, Florian Weimer <fweimer@redhat.com> wrote:
> * H. J. Lu:
>
>> I guess you knew that this issue was independent of my new functions.
>> You will get the same error regardless of what the get_free body has.
>
> Yes, the check is certainly overly conservative.  I thought we want to
> remove it.  Don't we trigger it in glibc in a few places?  If the check
> is gone, then I think we will see incorrect results from the new
> interface.
>
> I think we are very consistent right now when it comes to relocations in
> IFUNC handlers.  I want to see this settled before adding something that
> requires a relocation which is (among other things) targeted at IFUNC
> resolvers.
>

<sys/platform/x86.h> isn't targeted for IFUNC.   My first use is to add
x86_tsc_to_ns and x86_ns_to_tsc.   I am enclosing 2 patches here.

Comments

Florian Weimer Oct. 24, 2018, 12:43 p.m. UTC | #1
* H. J. Lu:

> On 10/24/18, Florian Weimer <fweimer@redhat.com> wrote:
>> * H. J. Lu:
>>
>>> I guess you knew that this issue was independent of my new functions.
>>> You will get the same error regardless of what the get_free body has.
>>
>> Yes, the check is certainly overly conservative.  I thought we want to
>> remove it.  Don't we trigger it in glibc in a few places?  If the check
>> is gone, then I think we will see incorrect results from the new
>> interface.
>>
>> I think we are very consistent right now when it comes to relocations in
>> IFUNC handlers.  I want to see this settled before adding something that
>> requires a relocation which is (among other things) targeted at IFUNC
>> resolvers.
>>
>
> <sys/platform/x86.h> isn't targeted for IFUNC.   My first use is to add
> x86_tsc_to_ns and x86_ns_to_tsc.   I am enclosing 2 patches here.

That's a generic interface which should rely on internal CPU flags.
What's worse, the cached flag isn't updated by the kernel TSC watchdog,
so applications will use a known-broken time source.

What's wrong with clock_gettime?  It handles all these details.

Thanks,
Florian
H.J. Lu Oct. 24, 2018, 10:57 p.m. UTC | #2
On 10/24/18, Florian Weimer <fweimer@redhat.com> wrote:
> * H. J. Lu:
>
>> On 10/24/18, Florian Weimer <fweimer@redhat.com> wrote:
>>> * H. J. Lu:
>>>
>>>> I guess you knew that this issue was independent of my new functions.
>>>> You will get the same error regardless of what the get_free body has.
>>>
>>> Yes, the check is certainly overly conservative.  I thought we want to
>>> remove it.  Don't we trigger it in glibc in a few places?  If the check
>>> is gone, then I think we will see incorrect results from the new
>>> interface.
>>>
>>> I think we are very consistent right now when it comes to relocations in
>>> IFUNC handlers.  I want to see this settled before adding something that
>>> requires a relocation which is (among other things) targeted at IFUNC
>>> resolvers.
>>>
>>
>> <sys/platform/x86.h> isn't targeted for IFUNC.   My first use is to add
>> x86_tsc_to_ns and x86_ns_to_tsc.   I am enclosing 2 patches here.
>
> That's a generic interface which should rely on internal CPU flags.
> What's worse, the cached flag isn't updated by the kernel TSC watchdog,
> so applications will use a known-broken time source.
>
> What's wrong with clock_gettime?  It handles all these details.
>

These are for cases where RDTSC/RDTSCP are preferred over
clock_gettime.
diff mbox

Patch

From d596a8620e40be7052329acdc1c4dc505f68e017 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Thu, 26 Jul 2018 13:46:05 -0700
Subject: [PATCH 2/2] sys/platform/x86.h: Add x86_tsc_to_ns/x86_ns_to_tsc

If "CPU_FEATURE_USABLE (TSC_To_NS)" evaluates true,

extern unsigned long long x86_tsc_to_ns (unsigned long long);
extern unsigned long long x86_ns_to_tsc (unsigned long long);

can be used to convert between time stamp counters (TSCs) and nanoseconds.

	* manual/platform.texi: Document x86_tsc_to_ns, x86_ns_to_tsc
	and TSC_To_NS.
	* sysdeps/mach/hurd/i386/libc.abilist: Add x86_ns_to_tsc and
	x86_tsc_to_ns.
	* sysdeps/unix/sysv/linux/i386/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/64/libc.abilist: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist: Likewise.
	* sysdeps/x86/Makefile (sysdep_routines): Add tsc-ns.
	(tests): Add tst-tsc-ns and tst-tsc-ns-static.
	(tests-static): Add tst-tsc-ns-static.
	* sysdeps/x86/Versions (libc::GLIBC_2.29): Add x86_tsc_to_ns
	and x86_ns_to_tsc.
	* sysdeps/x86/cpu-features.c (init_cpu_features): Update
	tsc_nccc_data and set TSC_To_NS_Usable if supported.
	* sysdeps/x86/cpu-features.h (tsc_nccc_info): New.
	(cpu_features): Add tsc_nccc_data.
	* sysdeps/x86/cpu-tunables.c (TUNABLE_CALLBACK (set_hwcaps)):
	Support TSC_To_NS_Usable.
	* sysdeps/x86/sys/platform/x86.h (x86_tsc_to_ns): New.
	(x86_ns_to_tsc): Likewise.
	(bit_arch_TSC_To_NS_Usable): Likewise.
	(index_arch_TSC_To_NS_Usable): Likewise.
	(bit_cpu_TSC_To_NS): Likewise.
	(index_cpu_TSC_To_NS): Likewise.
	(reg_TSC_To_NS): Likewise.
	(need_arch_feature_TSC_To_NS): Likewise.
	* sysdeps/x86/tsc-ns.c: New file.
	* sysdeps/x86/tst-tsc-ns-static.c: Likewise.
	* sysdeps/x86/tst-tsc-ns.c: Likewise.
	* sysdeps/x86/tst-x86-platform-1.c (do_test): Also check
	TSC_To_NS.
---
 manual/platform.texi                          | 14 +++-
 sysdeps/mach/hurd/i386/libc.abilist           |  2 +
 sysdeps/unix/sysv/linux/i386/libc.abilist     |  2 +
 .../unix/sysv/linux/x86_64/64/libc.abilist    |  2 +
 .../unix/sysv/linux/x86_64/x32/libc.abilist   |  2 +
 sysdeps/x86/Makefile                          |  5 ++
 sysdeps/x86/Versions                          |  6 ++
 sysdeps/x86/cpu-features.c                    | 41 ++++++++++++
 sysdeps/x86/cpu-features.h                    | 13 ++++
 sysdeps/x86/cpu-tunables.c                    |  9 ++-
 sysdeps/x86/sys/platform/x86.h                | 17 +++++
 sysdeps/x86/tsc-ns.c                          | 64 +++++++++++++++++++
 sysdeps/x86/tst-tsc-ns-static.c               |  1 +
 sysdeps/x86/tst-tsc-ns.c                      | 51 +++++++++++++++
 sysdeps/x86/tst-x86-platform-1.c              |  2 +
 15 files changed, 227 insertions(+), 4 deletions(-)
 create mode 100644 sysdeps/x86/tsc-ns.c
 create mode 100644 sysdeps/x86/tst-tsc-ns-static.c
 create mode 100644 sysdeps/x86/tst-tsc-ns.c

diff --git a/manual/platform.texi b/manual/platform.texi
index b0faa61a67..a3f43a1a1f 100644
--- a/manual/platform.texi
+++ b/manual/platform.texi
@@ -151,6 +151,18 @@  Internal function used by @code{HAS_CPU_FEATURE}.
 Internal function used by @code{CPU_FEATURE_USABLE}.
 @end deftypefun
 
+@deftypefun {unsigned long long} x86_tsc_to_ns (unsigned long long)
+
+Convert time stamp counter (TSC) to nanosecond if
+@code{CPU_FEATURE_USABLE (TSC_To_NS)} evaluates to true.
+@end deftypefun
+
+@deftypefun {unsigned long long} x86_ns_to_tsc (unsigned long long)
+
+Convert nanosecond to time stamp counter (TSC) if
+@code{CPU_FEATURE_USABLE (TSC_To_NS)} evaluates to true.
+@end deftypefun
+
 @defmac HAS_CPU_FEATURE(name)
 
 Evaluate to true if the CPU feature @code{name} is supported as indicated
@@ -606,7 +618,7 @@  The supported features are:
 @item
 @code{TBM} @tab @code{TSC} @tab @code{VAES} @tab @code{VPCLMULQDQ}
 @item
-@code{XOP} @tab @code{XSAVE} @tab @code{XSAVEC}
+@code{XOP} @tab @code{XSAVE} @tab @code{XSAVEC} @tab @code{TSC_To_NS}
 @end multitable
 
 @end defmac
diff --git a/sysdeps/mach/hurd/i386/libc.abilist b/sysdeps/mach/hurd/i386/libc.abilist
index e3fc05137b..deadfda6a9 100644
--- a/sysdeps/mach/hurd/i386/libc.abilist
+++ b/sysdeps/mach/hurd/i386/libc.abilist
@@ -2038,6 +2038,8 @@  GLIBC_2.27 wcstof64x_l F
 GLIBC_2.28 fcntl64 F
 GLIBC_2.28 renameat2 F
 GLIBC_2.28 statx F
+GLIBC_2.29 x86_ns_to_tsc F
+GLIBC_2.29 x86_tsc_to_ns F
 GLIBC_2.3 __ctype_b_loc F
 GLIBC_2.3 __ctype_tolower_loc F
 GLIBC_2.3 __ctype_toupper_loc F
diff --git a/sysdeps/unix/sysv/linux/i386/libc.abilist b/sysdeps/unix/sysv/linux/i386/libc.abilist
index 9762c81365..f499b74acc 100644
--- a/sysdeps/unix/sysv/linux/i386/libc.abilist
+++ b/sysdeps/unix/sysv/linux/i386/libc.abilist
@@ -2045,6 +2045,8 @@  GLIBC_2.28 thrd_current F
 GLIBC_2.28 thrd_equal F
 GLIBC_2.28 thrd_sleep F
 GLIBC_2.28 thrd_yield F
+GLIBC_2.29 x86_ns_to_tsc F
+GLIBC_2.29 x86_tsc_to_ns F
 GLIBC_2.3 __ctype_b_loc F
 GLIBC_2.3 __ctype_tolower_loc F
 GLIBC_2.3 __ctype_toupper_loc F
diff --git a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
index 816e4a7426..436c18162b 100644
--- a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
@@ -1895,6 +1895,8 @@  GLIBC_2.28 thrd_current F
 GLIBC_2.28 thrd_equal F
 GLIBC_2.28 thrd_sleep F
 GLIBC_2.28 thrd_yield F
+GLIBC_2.29 x86_ns_to_tsc F
+GLIBC_2.29 x86_tsc_to_ns F
 GLIBC_2.3 __ctype_b_loc F
 GLIBC_2.3 __ctype_tolower_loc F
 GLIBC_2.3 __ctype_toupper_loc F
diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
index 6fee16a850..61a23fb686 100644
--- a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
@@ -2146,3 +2146,5 @@  GLIBC_2.28 thrd_current F
 GLIBC_2.28 thrd_equal F
 GLIBC_2.28 thrd_sleep F
 GLIBC_2.28 thrd_yield F
+GLIBC_2.29 x86_ns_to_tsc F
+GLIBC_2.29 x86_tsc_to_ns F
diff --git a/sysdeps/x86/Makefile b/sysdeps/x86/Makefile
index 1e759d3efc..b2433c4317 100644
--- a/sysdeps/x86/Makefile
+++ b/sysdeps/x86/Makefile
@@ -26,6 +26,11 @@  endif
 
 ifeq ($(subdir),misc)
 sysdep_headers += sys/platform/x86.h
+
+sysdep_routines += tsc-ns
+
+tests += tst-tsc-ns tst-tsc-ns-static
+tests-static += tst-tsc-ns-static
 endif
 
 ifeq ($(subdir),setjmp)
diff --git a/sysdeps/x86/Versions b/sysdeps/x86/Versions
index 92ab4d93a3..7481c6ec56 100644
--- a/sysdeps/x86/Versions
+++ b/sysdeps/x86/Versions
@@ -1,3 +1,9 @@ 
+libc {
+  GLIBC_2.29 {
+    x86_tsc_to_ns; x86_ns_to_tsc;
+  }
+}
+
 ld {
   GLIBC_2.29 {
     x86_get_cpuid_registers; x86_get_arch_feature;
diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
index f812f406fd..31e3474e38 100644
--- a/sysdeps/x86/cpu-features.c
+++ b/sysdeps/x86/cpu-features.c
@@ -423,6 +423,47 @@  init_cpu_features (struct cpu_features *cpu_features)
       else
 	cpu_features->feature[index_arch_Prefer_No_AVX512]
 	  |= bit_arch_Prefer_No_AVX512;
+
+      if (cpu_features->max_cpuid >= 0x15
+	  && CPU_FEATURES_CPU_P (cpu_features, INVARIANT_TSC))
+	{
+	  unsigned int frequency = 0;
+	  unsigned int nominator = 0;
+
+	  __cpuid (0x15,
+		   cpu_features->tsc_nccc_data.denominator,
+		   nominator, frequency, edx);
+	  if (nominator != 0 && frequency == 0 && family == 6)
+	    switch (model)
+	      {
+	      case 0x55:
+		/* Skylake server is 25 MHz.  */
+		frequency = 25 * 1000 * 1000;
+		break;
+	      case 0x5c:
+		/* Goldmont is 19.2 MHz.  */
+		frequency = 19.2 * 1000 * 1000;
+		break;
+	      default:
+		if (CPU_FEATURES_CPU_P (cpu_features, AVX2)
+		    && CPU_FEATURES_CPU_P (cpu_features, XSAVEC)
+		    && CPU_FEATURES_CPU_P (cpu_features,
+					   XGETBV_ECX_1))
+		  {
+		    /* Skylake client is 24 MHz.  */
+		    frequency = 24 * 1000 * 1000;
+		    break;
+		  }
+	      }
+	  if (frequency != 0)
+	    {
+	      /* Store frequency as kHz.  */
+	      cpu_features->tsc_nccc_data.frequency = frequency / 1000;
+	      cpu_features->tsc_nccc_data.nominator = nominator;
+	      cpu_features->feature[index_arch_TSC_To_NS_Usable]
+		|= bit_arch_TSC_To_NS_Usable;
+	    }
+	}
     }
   /* This spells out "AuthenticAMD".  */
   else if (ebx == 0x68747541 && ecx == 0x444d4163 && edx == 0x69746e65)
diff --git a/sysdeps/x86/cpu-features.h b/sysdeps/x86/cpu-features.h
index 9ffa77e040..2db5249018 100644
--- a/sysdeps/x86/cpu-features.h
+++ b/sysdeps/x86/cpu-features.h
@@ -70,6 +70,17 @@  enum cpu_features_kind
     arch_kind_other
   };
 
+/* Time Stamp Counter and Nominal Core Crystal Clock Information.  */
+struct tsc_nccc_info
+{
+  /* The denominator of the TSC/core crystal clock ratio.  */
+  unsigned int denominator;
+  /* The numerator of the TSC/core crystal clock ratio.  */
+  unsigned int nominator;
+  /* The nominal frequency of the core crystal clock in Hz.  */
+  unsigned int frequency;
+};
+
 struct cpu_features
 {
   enum cpu_features_kind kind;
@@ -98,6 +109,8 @@  struct cpu_features
   unsigned long int shared_cache_size;
   /* Threshold to use non temporal store.  */
   unsigned long int non_temporal_threshold;
+  /* Time Stamp Counter and Nominal Core Crystal Clock Information.  */
+  struct tsc_nccc_info tsc_nccc_data;
 };
 
 /* Used from outside of glibc to get access to the CPU features
diff --git a/sysdeps/x86/cpu-tunables.c b/sysdeps/x86/cpu-tunables.c
index 8e92358c67..89df38c870 100644
--- a/sysdeps/x86/cpu-tunables.c
+++ b/sysdeps/x86/cpu-tunables.c
@@ -271,11 +271,14 @@  TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp)
 				       disable, 15);
 	  break;
 	case 16:
+	  if (disable)
 	    {
-	      CHECK_GLIBC_IFUNC_ARCH_NEED_ARCH_BOTH
-		(n, cpu_features, Prefer_No_AVX512, AVX512F_Usable,
-		 disable, 16);
+	      CHECK_GLIBC_IFUNC_ARCH_OFF (n, cpu_features,
+					  TSC_To_NS_Usable, 16);
 	    }
+	  CHECK_GLIBC_IFUNC_ARCH_NEED_ARCH_BOTH
+	    (n, cpu_features, Prefer_No_AVX512, AVX512F_Usable,
+	     disable, 16);
 	  break;
 	case 18:
 	    {
diff --git a/sysdeps/x86/sys/platform/x86.h b/sysdeps/x86/sys/platform/x86.h
index a2c5c7074d..168081e08a 100644
--- a/sysdeps/x86/sys/platform/x86.h
+++ b/sysdeps/x86/sys/platform/x86.h
@@ -59,6 +59,9 @@  extern const struct cpuid_registers *x86_get_cpuid_registers
 extern unsigned int x86_get_arch_feature (unsigned int)
      __attribute__ ((const));
 
+extern unsigned long long x86_tsc_to_ns (unsigned long long);
+extern unsigned long long x86_ns_to_tsc (unsigned long long);
+
 /* HAS_CPU_FEATURE evaluates to true if CPU supports the feature.  */
 #define HAS_CPU_FEATURE(name) \
  ((x86_get_cpuid_registers (index_cpu_##name)->reg_##name \
@@ -96,6 +99,7 @@  extern unsigned int x86_get_arch_feature (unsigned int)
 #define bit_arch_VPCLMULQDQ_Usable		(1u << 20)
 #define bit_arch_XOP_Usable			(1u << 21)
 #define bit_arch_XSAVEC_Usable			(1u << 22)
+#define bit_arch_TSC_To_NS_Usable		(1u << 23)
 
 #define index_arch_AVX_Usable			FEATURE_INDEX_1
 #define index_arch_AVX2_Usable			FEATURE_INDEX_1
@@ -120,6 +124,7 @@  extern unsigned int x86_get_arch_feature (unsigned int)
 #define index_arch_VPCLMULQDQ_Usable		FEATURE_INDEX_1
 #define index_arch_XOP_Usable			FEATURE_INDEX_1
 #define index_arch_XSAVEC_Usable		FEATURE_INDEX_1
+#define index_arch_TSC_To_NS_Usable		FEATURE_INDEX_1
 
 /* Unused.  Compiler will optimize them out.  */
 #define bit_arch_SSE3_Usable			(1u << 0)
@@ -234,6 +239,18 @@  extern unsigned int x86_get_arch_feature (unsigned int)
 #define index_arch_INVARIANT_TSC_Usable		FEATURE_INDEX_1
 #define index_arch_WBNOINVD_Usable		FEATURE_INDEX_1
 
+/* Unused.  Compiler will optimize them out.  */
+#define bit_cpu_TSC_To_NS			(1u << 0)
+
+/* Unused.  Compiler will optimize them out.  */
+#define index_cpu_TSC_To_NS			COMMON_CPUID_INDEX_1
+
+/* Unused.  Compiler will optimize them out.  */
+#define reg_TSC_To_NS				eax
+
+/* There is no CPUID bit.  */
+#define	need_arch_feature_TSC_To_NS		1
+
 /* COMMON_CPUID_INDEX_1.  */
 
 /* ECX.  */
diff --git a/sysdeps/x86/tsc-ns.c b/sysdeps/x86/tsc-ns.c
new file mode 100644
index 0000000000..ba1e677382
--- /dev/null
+++ b/sysdeps/x86/tsc-ns.c
@@ -0,0 +1,64 @@ 
+/* Conversion functions between TSCs and nanoseconds.
+   Copyright (C) 2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <ldsodefs.h>
+
+static struct tsc_nccc_info tsc_nccc_data;
+
+static void
+__attribute__((constructor))
+init_tsc_nccc_data (void)
+{
+  const struct cpu_features* cpu_features = __get_cpu_features ();
+  if (CPU_FEATURES_ARCH_P (cpu_features, TSC_To_NS_Usable))
+    tsc_nccc_data = cpu_features->tsc_nccc_data;
+}
+
+unsigned long long
+x86_tsc_to_ns (unsigned long long tsc)
+{
+  if (__glibc_unlikely (tsc_nccc_data.frequency == 0))
+    return 0;
+
+  /* Use double to avoid integer overflow.  */
+  double tmp = tsc;
+  tmp *= tsc_nccc_data.denominator * 1000000;
+  tmp /= tsc_nccc_data.frequency;
+  unsigned long long ns = tmp;
+  /* Round to the closest integer.  */
+  ns += tsc_nccc_data.nominator / 2;
+  return ns / tsc_nccc_data.nominator;
+
+}
+
+unsigned long long
+x86_ns_to_tsc (unsigned long long ns)
+{
+  if (__glibc_unlikely (tsc_nccc_data.frequency == 0))
+    return 0;
+
+  /* Use double to avoid integer overflow.  */
+  double tmp = ns;
+  tmp *= tsc_nccc_data.frequency;
+  tmp *= tsc_nccc_data.nominator;
+  tmp /= tsc_nccc_data.denominator;
+  unsigned long long tsc = tmp;
+  /* Round to the closest integer.  */
+  ns += 1000000 / 2;
+  return tsc / 1000000;
+}
diff --git a/sysdeps/x86/tst-tsc-ns-static.c b/sysdeps/x86/tst-tsc-ns-static.c
new file mode 100644
index 0000000000..ceb5ebc682
--- /dev/null
+++ b/sysdeps/x86/tst-tsc-ns-static.c
@@ -0,0 +1 @@ 
+#include "tst-tsc-ns.c"
diff --git a/sysdeps/x86/tst-tsc-ns.c b/sysdeps/x86/tst-tsc-ns.c
new file mode 100644
index 0000000000..b3a11f311c
--- /dev/null
+++ b/sysdeps/x86/tst-tsc-ns.c
@@ -0,0 +1,51 @@ 
+/* Test cases for x86 conversion functions between TSCs and nanoseconds.
+   Copyright (C) 2015-2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <errno.h>
+#include <x86intrin.h>
+#include <sys/platform/x86.h>
+
+static int do_test (void);
+
+#include <support/test-driver.c>
+
+static int
+do_test (void)
+{
+  if (!CPU_FEATURE_USABLE (TSC_To_NS))
+    return EXIT_UNSUPPORTED;
+
+  unsigned long long start_tscs, end_tscs, diff_tscs;
+  unsigned long long diff_nanoseconds;
+  start_tscs = _rdtsc ();
+  end_tscs = _rdtsc ();
+  diff_tscs = end_tscs - start_tscs;
+  diff_nanoseconds = x86_tsc_to_ns (diff_tscs);
+
+  printf ("Diff: %lld (TSCs) -> %lld (nanoseconds)\n",
+	  diff_tscs, diff_nanoseconds);
+
+  diff_tscs = x86_ns_to_tsc (diff_nanoseconds);
+
+  printf ("Diff: %lld (nanoseconds) -> %lld (TSCs)\n",
+	  diff_nanoseconds, diff_tscs);
+
+  return EXIT_SUCCESS;
+}
diff --git a/sysdeps/x86/tst-x86-platform-1.c b/sysdeps/x86/tst-x86-platform-1.c
index 56c2c8c8c1..6c572f25c6 100644
--- a/sysdeps/x86/tst-x86-platform-1.c
+++ b/sysdeps/x86/tst-x86-platform-1.c
@@ -258,6 +258,8 @@  do_test (void)
   CHECK_CPU_FEATURE_USABLE (INVARIANT_TSC);
   CHECK_CPU_FEATURE_USABLE (WBNOINVD);
 
+  CHECK_CPU_FEATURE_USABLE (TSC_To_NS);
+
   return 0;
 }
 
-- 
2.17.2