From 18dcb0934217628711c5b1d22fd6d7635e683e3f Mon Sep 17 00:00:00 2001
From: Fernando Sahmkow
Date: Tue, 25 Feb 2020 12:28:55 -0400
Subject: HostTiming: Pause the hardware clock on pause.

---
 src/common/x64/native_clock.cpp | 7 +++++++
 src/common/x64/native_clock.h   | 2 ++
 2 files changed, 9 insertions(+)

(limited to 'src/common/x64')

diff --git a/src/common/x64/native_clock.cpp b/src/common/x64/native_clock.cpp
index 26d4d0ba6..926f92ff8 100644
--- a/src/common/x64/native_clock.cpp
+++ b/src/common/x64/native_clock.cpp
@@ -65,6 +65,13 @@ u64 NativeClock::GetRTSC() {
     return accumulated_ticks;
 }
 
+void NativeClock::Pause(bool is_paused) {
+    if (!is_paused) {
+        _mm_mfence();
+        last_measure = __rdtsc();
+    }
+}
+
 std::chrono::nanoseconds NativeClock::GetTimeNS() {
     const u64 rtsc_value = GetRTSC();
     return std::chrono::nanoseconds{MultiplyAndDivide64(rtsc_value, 1000000000, rtsc_frequency)};
diff --git a/src/common/x64/native_clock.h b/src/common/x64/native_clock.h
index b58cf9f5a..3851f8fc2 100644
--- a/src/common/x64/native_clock.h
+++ b/src/common/x64/native_clock.h
@@ -26,6 +26,8 @@ public:
 
     u64 GetCPUCycles() override;
 
+    void Pause(bool is_paused) override;
+
 private:
     u64 GetRTSC();
 
-- 
cgit v1.2.3


From 534466754f381e90f5f6475a0c02031242a5c256 Mon Sep 17 00:00:00 2001
From: Fernando Sahmkow
Date: Sat, 21 Mar 2020 12:23:13 -0400
Subject: X64 Clock: Reduce accuracy to be less or equal to guest accuracy.

---
 src/common/x64/native_clock.cpp | 3 ++-
 src/common/x64/native_clock.h   | 5 +++++
 2 files changed, 7 insertions(+), 1 deletion(-)

(limited to 'src/common/x64')

diff --git a/src/common/x64/native_clock.cpp b/src/common/x64/native_clock.cpp
index 926f92ff8..f1bc60fd2 100644
--- a/src/common/x64/native_clock.cpp
+++ b/src/common/x64/native_clock.cpp
@@ -62,7 +62,8 @@ u64 NativeClock::GetRTSC() {
     }
     accumulated_ticks += diff;
     rtsc_serialize.unlock();
-    return accumulated_ticks;
+    /// The clock cannot be more precise than the guest timer, remove the lower bits
+    return accumulated_ticks & inaccuracy_mask;
 }
 
 void NativeClock::Pause(bool is_paused) {
diff --git a/src/common/x64/native_clock.h b/src/common/x64/native_clock.h
index 3851f8fc2..e853094d2 100644
--- a/src/common/x64/native_clock.h
+++ b/src/common/x64/native_clock.h
@@ -31,6 +31,11 @@ public:
 private:
     u64 GetRTSC();
 
+    /// value used to reduce the native clocks accuracy as some apss rely on
+    /// undefined behavior where the level of accuracy in the clock shouldn't
+    /// be higher.
+    static constexpr u64 inaccuracy_mask = ~(0x100 - 1);
+
     SpinLock rtsc_serialize{};
     u64 last_measure{};
     u64 accumulated_ticks{};
-- 
cgit v1.2.3


From 31651523968312433ebd267a74e86689107a7023 Mon Sep 17 00:00:00 2001
From: Fernando Sahmkow
Date: Mon, 18 May 2020 13:08:53 -0400
Subject: Common/NativeClockx86: Reduce native clock accuracy further.

---
 src/common/x64/native_clock.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'src/common/x64')

diff --git a/src/common/x64/native_clock.h b/src/common/x64/native_clock.h
index e853094d2..891a3bbfd 100644
--- a/src/common/x64/native_clock.h
+++ b/src/common/x64/native_clock.h
@@ -34,7 +34,7 @@ private:
     /// value used to reduce the native clocks accuracy as some apss rely on
     /// undefined behavior where the level of accuracy in the clock shouldn't
     /// be higher.
-    static constexpr u64 inaccuracy_mask = ~(0x100 - 1);
+    static constexpr u64 inaccuracy_mask = ~(0x400 - 1);
 
     SpinLock rtsc_serialize{};
     u64 last_measure{};
-- 
cgit v1.2.3


From 2f8947583f2f0af4058600243d6c1d244e3c4890 Mon Sep 17 00:00:00 2001
From: Fernando Sahmkow
Date: Sat, 27 Jun 2020 18:20:06 -0400
Subject: Core/Common: Address Feedback.

---
 src/common/x64/native_clock.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

(limited to 'src/common/x64')

diff --git a/src/common/x64/native_clock.cpp b/src/common/x64/native_clock.cpp
index f1bc60fd2..424b39b1f 100644
--- a/src/common/x64/native_clock.cpp
+++ b/src/common/x64/native_clock.cpp
@@ -3,6 +3,7 @@
 // Refer to the license.txt file included.
 
 #include <chrono>
+#include <mutex>
 #include <thread>
 
 #ifdef _MSC_VER
@@ -52,7 +53,7 @@ NativeClock::NativeClock(u64 emulated_cpu_frequency, u64 emulated_clock_frequenc
 }
 
 u64 NativeClock::GetRTSC() {
-    rtsc_serialize.lock();
+    std::scoped_lock scope{rtsc_serialize};
     _mm_mfence();
     const u64 current_measure = __rdtsc();
     u64 diff = current_measure - last_measure;
@@ -61,7 +62,6 @@ u64 NativeClock::GetRTSC() {
         last_measure = current_measure;
     }
     accumulated_ticks += diff;
-    rtsc_serialize.unlock();
     /// The clock cannot be more precise than the guest timer, remove the lower bits
     return accumulated_ticks & inaccuracy_mask;
 }
-- 
cgit v1.2.3