svn commit: r264825 - head/sys/amd64/vmm/io

[Neel Natu]

Author: neel
Date: Wed Apr 23 16:50:40 2014
New Revision: 264825
URL: http://svnweb.freebsd.org/changeset/base/264825

Log:
  Change the vlapic timer frequency to be in the ballpark of contemporary
  hardware. This also decouples the vlapic emulation from the host's TSC
  frequency.
  
  Requested by:	grehan@

Modified:
  head/sys/amd64/vmm/io/vlapic.c

Modified: head/sys/amd64/vmm/io/vlapic.c
==============================================================================
--- head/sys/amd64/vmm/io/vlapic.c	Wed Apr 23 15:18:40 2014	(r264824)
+++ head/sys/amd64/vmm/io/vlapic.c	Wed Apr 23 16:50:40 2014	(r264825)
@@ -70,7 +70,12 @@ __FBSDID("$FreeBSD$");
 #define	VLAPIC_TIMER_UNLOCK(vlapic)	mtx_unlock_spin(&((vlapic)->timer_mtx))
 #define	VLAPIC_TIMER_LOCKED(vlapic)	mtx_owned(&((vlapic)->timer_mtx))
 
-#define VLAPIC_BUS_FREQ	tsc_freq
+/*
+ * APIC timer frequency:
+ * - arbitrary but chosen to be in the ballpark of contemporary hardware.
+ * - power-of-two to avoid loss of precision when converted to a bintime.
+ */
+#define VLAPIC_BUS_FREQ		(128 * 1024 * 1024)
 
 static __inline uint32_t
 vlapic_get_id(struct vlapic *vlapic)