svn commit: r278184 - in head/sys/x86: include x86

Bryan Venteicher bryanv at FreeBSD.org
Wed Feb 4 08:33:05 UTC 2015


Author: bryanv
Date: Wed Feb  4 08:33:04 2015
New Revision: 278184
URL: https://svnweb.freebsd.org/changeset/base/278184

Log:
  Add interface to derive a TSC frequency from the pvclock
  
  This can later use this to determine the TSC frequency like is done with
  VMware, instead of using a DELAY loop that is not always accurate in an VM.
  
  MFC after:	1 month

Modified:
  head/sys/x86/include/pvclock.h
  head/sys/x86/x86/pvclock.c

Modified: head/sys/x86/include/pvclock.h
==============================================================================
--- head/sys/x86/include/pvclock.h	Wed Feb  4 08:26:43 2015	(r278183)
+++ head/sys/x86/include/pvclock.h	Wed Feb  4 08:33:04 2015	(r278184)
@@ -51,6 +51,7 @@ struct pvclock_wall_clock {
 
 void		pvclock_resume(void);
 uint64_t	pvclock_get_last_cycles(void);
+uint64_t	pvclock_tsc_freq(struct pvclock_vcpu_time_info *ti);
 uint64_t	pvclock_get_timecount(struct pvclock_vcpu_time_info *ti);
 void		pvclock_get_wallclock(struct pvclock_wall_clock *wc,
 		    struct timespec *ts);

Modified: head/sys/x86/x86/pvclock.c
==============================================================================
--- head/sys/x86/x86/pvclock.c	Wed Feb  4 08:26:43 2015	(r278183)
+++ head/sys/x86/x86/pvclock.c	Wed Feb  4 08:33:04 2015	(r278184)
@@ -58,6 +58,21 @@ pvclock_get_last_cycles(void)
 	return (atomic_load_acq_64(&pvclock_last_cycles));
 }
 
+uint64_t
+pvclock_tsc_freq(struct pvclock_vcpu_time_info *ti)
+{
+	uint64_t freq;
+
+	freq = (1000000000ULL << 32) / ti->tsc_to_system_mul;
+
+	if (ti->tsc_shift < 0)
+		freq <<= -ti->tsc_shift;
+	else
+		freq >>= ti->tsc_shift;
+
+	return (freq);
+}
+
 /*
  * Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction,
  * yielding a 64-bit result.


More information about the svn-src-head mailing list