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>

1 files changed, 6 insertions, 4 deletions

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 55856b2310d3..dd3b82530145 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -352,8 +352,9 @@ static efi_status_t __init phys_efi_get_time(efi_time_t *tm,
         return status;
 }
 
-int efi_set_rtc_mmss(unsigned long nowtime)
+int efi_set_rtc_mmss(const struct timespec *now)
 {
+        unsigned long nowtime = now->tv_sec;
         efi_status_t    status;
         efi_time_t      eft;
         efi_time_cap_t  cap;
@@ -388,7 +389,7 @@ int efi_set_rtc_mmss(unsigned long nowtime)
         return 0;
 }
 
-unsigned long efi_get_time(void)
+void efi_get_time(struct timespec *now)
 {
         efi_status_t status;
         efi_time_t eft;
@@ -398,8 +399,9 @@ unsigned long efi_get_time(void)
         if (status != EFI_SUCCESS)
                 pr_err("Oops: efitime: can't read time!\n");
 
-        return mktime(eft.year, eft.month, eft.day, eft.hour,
-                      eft.minute, eft.second);
+        now->tv_sec = mktime(eft.year, eft.month, eft.day, eft.hour,
+                             eft.minute, eft.second);
+        now->tv_nsec = 0;
 }
 
 /*