Commit 3565184e authored by David Vrabel's avatar David Vrabel Committed by John Stultz
Browse files

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: default avatarDavid Vrabel <david.vrabel@citrix.com>
Signed-off-by: default avatarJohn Stultz <john.stultz@linaro.org>
parent 0a0a7e66

arch/x86/include/asm/mc146818rtc.h

+2 −2
Original line number Diff line number Diff line
@@ -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

arch/x86/include/asm/x86_init.h

+4 −2
Original line number Diff line number Diff line
@@ -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);

arch/x86/kernel/kvmclock.c

+3 −6
Original line number Diff line number Diff line
@@ -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;

}

arch/x86/kernel/rtc.c

+7 −10
Original line number Diff line number Diff line
@@ -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);

}

arch/x86/lguest/boot.c

+2 −2
Original line number Diff line number Diff line
@@ -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;

}



/*

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