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authorDavid Vrabel <david.vrabel@citrix.com>2013-05-13 21:56:06 +0400
committerJohn Stultz <john.stultz@linaro.org>2013-05-29 01:00:59 +0400
commit3565184ed0c1ea46bea5b792da5f72a83c43e49b (patch)
tree4846a589a6aa295634ef585e5637872f15c19993 /arch/x86/kernel/kvmclock.c
parent0a0a7e66fa269de78975ea8d4e825a66d92b8d70 (diff)
downloadlinux-3565184ed0c1ea46bea5b792da5f72a83c43e49b.tar.xz
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>
Diffstat (limited to 'arch/x86/kernel/kvmclock.c')
-rw-r--r--arch/x86/kernel/kvmclock.c9
1 files changed, 3 insertions, 6 deletions
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index d2c381280e3c..0db81ab511cc 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -48,10 +48,9 @@ static struct pvclock_wall_clock wall_clock;
* have elapsed since the hypervisor wrote the data. So we try to account for
* that with system time
*/
-static unsigned long kvm_get_wallclock(void)
+static void kvm_get_wallclock(struct timespec *now)
{
struct pvclock_vcpu_time_info *vcpu_time;
- struct timespec ts;
int low, high;
int cpu;
@@ -64,14 +63,12 @@ static unsigned long kvm_get_wallclock(void)
cpu = smp_processor_id();
vcpu_time = &hv_clock[cpu].pvti;
- pvclock_read_wallclock(&wall_clock, vcpu_time, &ts);
+ pvclock_read_wallclock(&wall_clock, vcpu_time, now);
preempt_enable();
-
- return ts.tv_sec;
}
-static int kvm_set_wallclock(unsigned long now)
+static int kvm_set_wallclock(const struct timespec *now)
{
return -1;
}