x86: Increase precision of x86_platform.get/set_wallclock()
All the virtualized platforms (KVM, lguest and Xen) have persistent
wallclocks that have more than one second of precision.
read_persistent_wallclock() and update_persistent_wallclock() allow
for nanosecond precision but their implementation on x86 with
x86_platform.get/set_wallclock() only allows for one second precision.
This means guests may see a wallclock time that is off by up to 1
second.
Make set_wallclock() and get_wallclock() take a struct timespec
parameter (which allows for nanosecond precision) so KVM and Xen
guests may start with a more accurate wallclock time and a Xen dom0
can maintain a more accurate wallclock for guests.
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c
index 198eb20..0aa2939 100644
--- a/arch/x86/kernel/rtc.c
+++ b/arch/x86/kernel/rtc.c
@@ -38,8 +38,9 @@
* jump to the next second precisely 500 ms later. Check the Motorola
* MC146818A or Dallas DS12887 data sheet for details.
*/
-int mach_set_rtc_mmss(unsigned long nowtime)
+int mach_set_rtc_mmss(const struct timespec *now)
{
+ unsigned long nowtime = now->tv_sec;
struct rtc_time tm;
int retval = 0;
@@ -58,7 +59,7 @@
return retval;
}
-unsigned long mach_get_cmos_time(void)
+void mach_get_cmos_time(struct timespec *now)
{
unsigned int status, year, mon, day, hour, min, sec, century = 0;
unsigned long flags;
@@ -107,7 +108,8 @@
} else
year += CMOS_YEARS_OFFS;
- return mktime(year, mon, day, hour, min, sec);
+ now->tv_sec = mktime(year, mon, day, hour, min, sec);
+ now->tv_nsec = 0;
}
/* Routines for accessing the CMOS RAM/RTC. */
@@ -135,18 +137,13 @@
int update_persistent_clock(struct timespec now)
{
- return x86_platform.set_wallclock(now.tv_sec);
+ return x86_platform.set_wallclock(&now);
}
/* not static: needed by APM */
void read_persistent_clock(struct timespec *ts)
{
- unsigned long retval;
-
- retval = x86_platform.get_wallclock();
-
- ts->tv_sec = retval;
- ts->tv_nsec = 0;
+ x86_platform.get_wallclock(ts);
}