[Xen-devel] [PATCH v4 1/7] introduce time managment in xtf

[Paul Semel <semelpaul@xxxxxxxxx>]

this file is introduce to be able to implement an inter domain
communication protocol over xenstore. For synchronization purpose, we do
really want to be able to "control" time

common/time.c: since_boot_time gets the time in nanoseconds from the
moment the VM has booted

Signed-off-by: Paul Semel <phentex@xxxxxxxxx>
---

Notes:
    v4:
    - moved rdtsc to arch/x86/include/arch/lib.h
    - added a rdtsc_ordered implementation to serialize rdtsc
    - simplified since_boot_time function
    - still need to have Andrew's scale_delta version

 arch/x86/include/arch/lib.h | 18 ++++++++++
 build/files.mk              |  1 +
 common/time.c               | 81 +++++++++++++++++++++++++++++++++++++++++++++
 include/xtf/time.h          | 24 ++++++++++++++
 4 files changed, 124 insertions(+)
 create mode 100644 common/time.c
 create mode 100644 include/xtf/time.h

diff --git a/arch/x86/include/arch/lib.h b/arch/x86/include/arch/lib.h
index 0045902..510cdb1 100644
--- a/arch/x86/include/arch/lib.h
+++ b/arch/x86/include/arch/lib.h
@@ -6,6 +6,7 @@
 #include <xen/arch-x86/xen.h>
 #include <arch/desc.h>
 #include <arch/msr.h>
+#include <arch/barrier.h>
 
 static inline void cpuid(uint32_t leaf,
                          uint32_t *eax, uint32_t *ebx,
@@ -374,6 +375,23 @@ static inline void write_xcr0(uint64_t xcr0)
     xsetbv(0, xcr0);
 }
 
+static inline uint64_t rdtsc(void)
+{
+    uint32_t lo, hi;
+
+    asm volatile("rdtsc": "=a"(lo), "=d"(hi));
+
+    return ((uint64_t)hi << 32) | lo;
+}
+
+static inline uint64_t rdtsc_ordered(void)
+{
+    rmb();
+    mb();
+
+    return rdtsc();
+}
+
 #endif /* XTF_X86_LIB_H */
 
 /*
diff --git a/build/files.mk b/build/files.mk
index 46b42d6..55ed1ca 100644
--- a/build/files.mk
+++ b/build/files.mk
@@ -16,6 +16,7 @@ obj-perarch += $(ROOT)/common/libc/vsnprintf.o
 obj-perarch += $(ROOT)/common/report.o
 obj-perarch += $(ROOT)/common/setup.o
 obj-perarch += $(ROOT)/common/xenbus.o
+obj-perarch += $(ROOT)/common/time.o
 
 obj-perenv += $(ROOT)/arch/x86/decode.o
 obj-perenv += $(ROOT)/arch/x86/desc.o
diff --git a/common/time.c b/common/time.c
new file mode 100644
index 0000000..79abc7e
--- /dev/null
+++ b/common/time.c
@@ -0,0 +1,81 @@
+#include <xtf/types.h>
+#include <xtf/traps.h>
+#include <xtf/time.h>
+
+#include <arch/barrier.h>
+#include <arch/lib.h>
+
+/* This function was taken from mini-os source code */
+/* It returns ((delta << shift) * mul_frac) >> 32 */
+static inline uint64_t scale_delta(uint64_t delta, uint32_t mul_frac, int 
shift)
+{
+    uint64_t product;
+#ifdef __i386__
+    uint32_t tmp1, tmp2;
+#endif
+
+    if ( shift < 0 )
+        delta >>= -shift;
+    else
+        delta <<= shift;
+
+#ifdef __i386__
+    __asm__ (
+            "mul  %5       ; "
+            "mov  %4,%%eax ; "
+            "mov  %%edx,%4 ; "
+            "mul  %5       ; "
+            "add  %4,%%eax ; "
+            "xor  %5,%5    ; "
+            "adc  %5,%%edx ; "
+            : "=A" (product), "=r" (tmp1), "=r" (tmp2)
+            : "a" ((uint32_t)delta), "1" ((uint32_t)(delta >> 32)), "2" 
(mul_frac) );
+#else
+    __asm__ (
+            "mul %%rdx ; shrd $32,%%rdx,%%rax"
+            : "=a" (product) : "0" (delta), "d" ((uint64_t)mul_frac) );
+#endif
+
+    return product;
+}
+
+
+uint64_t since_boot_time(void)
+{
+    uint32_t ver1, ver2;
+    uint64_t tsc_timestamp, system_time, tsc;
+    uint32_t tsc_to_system_mul;
+    int8_t tsc_shift;
+
+    do
+    {
+        ver1 = ACCESS_ONCE(shared_info.vcpu_info[0].time.version);
+        smp_rmb();
+
+        system_time = shared_info.vcpu_info[0].time.system_time;
+        tsc_timestamp = shared_info.vcpu_info[0].time.tsc_timestamp;
+        tsc_to_system_mul = shared_info.vcpu_info[0].time.tsc_to_system_mul;
+        tsc_shift = shared_info.vcpu_info[0].time.tsc_shift;
+        tsc = rdtsc_ordered();
+        smp_rmb();
+
+        ver2 = ACCESS_ONCE(shared_info.vcpu_info[0].time.version);
+    } while ( ver2 & 1 || ver1 != ver2 );
+
+
+    system_time += scale_delta(tsc - tsc_timestamp,
+                               tsc_to_system_mul,
+                               tsc_shift);
+
+    return system_time;
+}
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/include/xtf/time.h b/include/xtf/time.h
new file mode 100644
index 0000000..8180e07
--- /dev/null
+++ b/include/xtf/time.h
@@ -0,0 +1,24 @@
+/**
+ * @file include/xtf/time.h
+ *
+ * Time management
+ */
+#ifndef XTF_TIME_H
+# define XTF_TIME_H
+
+#include <xtf/types.h>
+
+/* Time from boot in nanoseconds */
+uint64_t since_boot_time(void);
+
+#endif /* XTF_TIME_H */
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
-- 
2.16.1


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