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>

8 files changed, 32 insertions, 41 deletions

diff --git a/arch/x86/include/asm/mc146818rtc.h b/arch/x86/include/asm/mc146818rtc.h
index d354fb781c57..a55c7efcc4ed 100644
--- a/arch/x86/include/asm/mc146818rtc.h
+++ b/arch/x86/include/asm/mc146818rtc.h
@@ -95,8 +95,8 @@ static inline unsigned char current_lock_cmos_reg(void)
 unsigned char rtc_cmos_read(unsigned char addr);
 void rtc_cmos_write(unsigned char val, unsigned char addr);
 
-extern int mach_set_rtc_mmss(unsigned long nowtime);
-extern unsigned long mach_get_cmos_time(void);
+extern int mach_set_rtc_mmss(const struct timespec *now);
+extern void mach_get_cmos_time(struct timespec *now);
 
 #define RTC_IRQ 8
 
diff --git a/arch/x86/include/asm/x86_init.h b/arch/x86/include/asm/x86_init.h
index d8d99222b36a..828a1565ba57 100644
--- a/arch/x86/include/asm/x86_init.h
+++ b/arch/x86/include/asm/x86_init.h
@@ -142,6 +142,8 @@ struct x86_cpuinit_ops {
         void (*fixup_cpu_id)(struct cpuinfo_x86 *c, int node);
 };
 
+struct timespec;
+
 /**
  * struct x86_platform_ops - platform specific runtime functions
  * @calibrate_tsc:              calibrate TSC
@@ -156,8 +158,8 @@ struct x86_cpuinit_ops {
  */
 struct x86_platform_ops {
         unsigned long (*calibrate_tsc)(void);
-        unsigned long (*get_wallclock)(void);
-        int (*set_wallclock)(unsigned long nowtime);
+        void (*get_wallclock)(struct timespec *ts);
+        int (*set_wallclock)(const struct timespec *ts);
         void (*iommu_shutdown)(void);
         bool (*is_untracked_pat_range)(u64 start, u64 end);
         void (*nmi_init)(void);
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;
 }
diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c
index 198eb201ed3b..0aa29394ed6f 100644
--- a/arch/x86/kernel/rtc.c
+++ b/arch/x86/kernel/rtc.c
@@ -38,8 +38,9 @@ EXPORT_SYMBOL(rtc_lock);
  * 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 @@ int mach_set_rtc_mmss(unsigned long nowtime)
         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 @@ unsigned long mach_get_cmos_time(void)
         } 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 @@ EXPORT_SYMBOL(rtc_cmos_write);
 
 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);
 }
 
 
diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index 7114c63f047d..8424d5adcfa2 100644
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -882,9 +882,9 @@ int lguest_setup_irq(unsigned int irq)
  * It would be far better for everyone if the Guest had its own clock, but
  * until then the Host gives us the time on every interrupt.
  */
-static unsigned long lguest_get_wallclock(void)
+static void lguest_get_wallclock(struct timespec *now)
 {
-        return lguest_data.time.tv_sec;
+        *now = lguest_data.time;
 }
 
 /*
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;
 }
 
 /*
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 3d88bfdf9e1c..a1947ac2da82 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -191,32 +191,25 @@ static void xen_read_wallclock(struct timespec *ts)
         put_cpu_var(xen_vcpu);
 }
 
-static unsigned long xen_get_wallclock(void)
+static void xen_get_wallclock(struct timespec *now)
 {
-        struct timespec ts;
-
-        xen_read_wallclock(&ts);
-        return ts.tv_sec;
+        xen_read_wallclock(now);
 }
 
-static int xen_set_wallclock(unsigned long now)
+static int xen_set_wallclock(const struct timespec *now)
 {
         struct xen_platform_op op;
-        int rc;
 
         /* do nothing for domU */
         if (!xen_initial_domain())
                 return -1;
 
         op.cmd = XENPF_settime;
-        op.u.settime.secs = now;
-        op.u.settime.nsecs = 0;
+        op.u.settime.secs = now->tv_sec;
+        op.u.settime.nsecs = now->tv_nsec;
         op.u.settime.system_time = xen_clocksource_read();
 
-        rc = HYPERVISOR_dom0_op(&op);
-        WARN(rc != 0, "XENPF_settime failed: now=%ld\n", now);
-
-        return rc;
+        return HYPERVISOR_dom0_op(&op);
 }
 
 static struct clocksource xen_clocksource __read_mostly = {
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 2bc0ad78d058..0068bba6f8b6 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -594,8 +594,8 @@ extern u64 efi_mem_attribute (unsigned long phys_addr, unsigned long size);
 extern int __init efi_uart_console_only (void);
 extern void efi_initialize_iomem_resources(struct resource *code_resource,
                 struct resource *data_resource, struct resource *bss_resource);
-extern unsigned long efi_get_time(void);
-extern int efi_set_rtc_mmss(unsigned long nowtime);
+extern void efi_get_time(struct timespec *now);
+extern int efi_set_rtc_mmss(const struct timespec *now);
 extern void efi_reserve_boot_services(void);
 extern struct efi_memory_map memmap;