[linux-2.6-block.git] / arch / x86 / kernel / pvclock.c

/*  paravirtual clock -- common code used by kvm/xen

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/

#include <linux/kernel.h>
#include <linux/percpu.h>
#include <asm/pvclock.h>

/*
 * These are perodically updated
 *    xen: magic shared_info page
 *    kvm: gpa registered via msr
 * and then copied here.
 */
struct pvclock_shadow_time {
	u64 tsc_timestamp;     /* TSC at last update of time vals.  */
	u64 system_timestamp;  /* Time, in nanosecs, since boot.    */
	u32 tsc_to_nsec_mul;
	int tsc_shift;
	u32 version;
};

/*
 * Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction,
 * yielding a 64-bit result.
 */
static inline u64 scale_delta(u64 delta, u32 mul_frac, int shift)
{
	u64 product;
#ifdef __i386__
	u32 tmp1, tmp2;
#endif

	if (shift < 0)
		delta >>= -shift;
	else
		delta <<= shift;

#ifdef __i386__
	__asm__ (
		"mul  %5       ; "
		"mov  %4,%%eax ; "
		"mov  %%edx,%4 ; "
		"mul  %5       ; "
		"xor  %5,%5    ; "
		"add  %4,%%eax ; "
		"adc  %5,%%edx ; "
		: "=A" (product), "=r" (tmp1), "=r" (tmp2)
		: "a" ((u32)delta), "1" ((u32)(delta >> 32)), "2" (mul_frac) );
#elif __x86_64__
	__asm__ (
		"mul %%rdx ; shrd $32,%%rdx,%%rax"
		: "=a" (product) : "0" (delta), "d" ((u64)mul_frac) );
#else
#error implement me!
#endif

	return product;
}

static u64 pvclock_get_nsec_offset(struct pvclock_shadow_time *shadow)
{
	u64 delta = native_read_tsc() - shadow->tsc_timestamp;
	return scale_delta(delta, shadow->tsc_to_nsec_mul, shadow->tsc_shift);
}

/*
 * Reads a consistent set of time-base values from hypervisor,
 * into a shadow data area.
 */
static unsigned pvclock_get_time_values(struct pvclock_shadow_time *dst,
					struct pvclock_vcpu_time_info *src)
{
	do {
		dst->version = src->version;
		rmb();		/* fetch version before data */
		dst->tsc_timestamp     = src->tsc_timestamp;
		dst->system_timestamp  = src->system_time;
		dst->tsc_to_nsec_mul   = src->tsc_to_system_mul;
		dst->tsc_shift         = src->tsc_shift;
		rmb();		/* test version after fetching data */
	} while ((src->version & 1) || (dst->version != src->version));

	return dst->version;
}

cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
{
	struct pvclock_shadow_time shadow;
	unsigned version;
	cycle_t ret, offset;

	do {
		version = pvclock_get_time_values(&shadow, src);
		barrier();
		offset = pvclock_get_nsec_offset(&shadow);
		ret = shadow.system_timestamp + offset;
		barrier();
	} while (version != src->version);

	return ret;
}

void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock,
			    struct pvclock_vcpu_time_info *vcpu_time,
			    struct timespec *ts)
{
	u32 version;
	u64 delta;
	struct timespec now;

	/* get wallclock at system boot */
	do {
		version = wall_clock->version;
		rmb();		/* fetch version before time */
		now.tv_sec  = wall_clock->sec;
		now.tv_nsec = wall_clock->nsec;
		rmb();		/* fetch time before checking version */
	} while ((wall_clock->version & 1) || (version != wall_clock->version));

	delta = pvclock_clocksource_read(vcpu_time);	/* time since system boot */
	delta += now.tv_sec * (u64)NSEC_PER_SEC + now.tv_nsec;

	now.tv_nsec = do_div(delta, NSEC_PER_SEC);
	now.tv_sec = delta;

	set_normalized_timespec(ts, now.tv_sec, now.tv_nsec);
}
Commit	Line	Data
7af192c9 GH	1	/* paravirtual clock -- common code used by kvm/xen
	2
	3	This program is free software; you can redistribute it and/or modify
	4	it under the terms of the GNU General Public License as published by
	5	the Free Software Foundation; either version 2 of the License, or
	6	(at your option) any later version.
	7
	8	This program is distributed in the hope that it will be useful,
	9	but WITHOUT ANY WARRANTY; without even the implied warranty of
	10	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	11	GNU General Public License for more details.
	12
	13	You should have received a copy of the GNU General Public License
	14	along with this program; if not, write to the Free Software
	15	Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
	16	*/
	17
	18	#include <linux/kernel.h>
	19	#include <linux/percpu.h>
	20	#include <asm/pvclock.h>
	21
	22	/*
	23	* These are perodically updated
	24	* xen: magic shared_info page
	25	* kvm: gpa registered via msr
	26	* and then copied here.
	27	*/
	28	struct pvclock_shadow_time {
	29	u64 tsc_timestamp; /* TSC at last update of time vals. */
	30	u64 system_timestamp; /* Time, in nanosecs, since boot. */
	31	u32 tsc_to_nsec_mul;
	32	int tsc_shift;
	33	u32 version;
	34	};
	35
	36	/*
	37	* Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction,
	38	* yielding a 64-bit result.
	39	*/
	40	static inline u64 scale_delta(u64 delta, u32 mul_frac, int shift)
	41	{
	42	u64 product;
	43	#ifdef __i386__
	44	u32 tmp1, tmp2;
	45	#endif
	46
	47	if (shift < 0)
	48	delta >>= -shift;
	49	else
	50	delta <<= shift;
	51
	52	#ifdef __i386__
	53	__asm__ (
	54	"mul %5 ; "
	55	"mov %4,%%eax ; "
	56	"mov %%edx,%4 ; "
	57	"mul %5 ; "
	58	"xor %5,%5 ; "
	59	"add %4,%%eax ; "
	60	"adc %5,%%edx ; "
	61	: "=A" (product), "=r" (tmp1), "=r" (tmp2)
	62	: "a" ((u32)delta), "1" ((u32)(delta >> 32)), "2" (mul_frac) );
	63	#elif __x86_64__
	64	__asm__ (
65	"mul %%rdx ; shrd $32,%%rdx,%%rax"
66	: "=a" (product) : "0" (delta), "d" ((u64)mul_frac) );
67	#else
68	#error implement me!
69	#endif
70
71	return product;
72	}
73
74	static u64 pvclock_get_nsec_offset(struct pvclock_shadow_time *shadow)
75	{
76	u64 delta = native_read_tsc() - shadow->tsc_timestamp;
77	return scale_delta(delta, shadow->tsc_to_nsec_mul, shadow->tsc_shift);
78	}
79
80	/*
81	* Reads a consistent set of time-base values from hypervisor,
82	* into a shadow data area.
83	*/
84	static unsigned pvclock_get_time_values(struct pvclock_shadow_time *dst,
85	struct pvclock_vcpu_time_info *src)
86	{
87	do {
88	dst->version = src->version;
89	rmb(); /* fetch version before data */
90	dst->tsc_timestamp = src->tsc_timestamp;
91	dst->system_timestamp = src->system_time;
92	dst->tsc_to_nsec_mul = src->tsc_to_system_mul;
93	dst->tsc_shift = src->tsc_shift;
94	rmb(); /* test version after fetching data */
95	} while ((src->version & 1) \|\| (dst->version != src->version));
96
97	return dst->version;
98	}
99
100	cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
101	{
102	struct pvclock_shadow_time shadow;
103	unsigned version;
104	cycle_t ret, offset;
105
106	do {
107	version = pvclock_get_time_values(&shadow, src);
108	barrier();
109	offset = pvclock_get_nsec_offset(&shadow);
110	ret = shadow.system_timestamp + offset;
111	barrier();
112	} while (version != src->version);
113
114	return ret;
115	}
116
117	void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock,
118	struct pvclock_vcpu_time_info *vcpu_time,
119	struct timespec *ts)
120	{
121	u32 version;
122	u64 delta;
123	struct timespec now;
124
125	/* get wallclock at system boot */
126	do {
127	version = wall_clock->version;
128	rmb(); /* fetch version before time */
129	now.tv_sec = wall_clock->sec;
130	now.tv_nsec = wall_clock->nsec;
131	rmb(); /* fetch time before checking version */
132	} while ((wall_clock->version & 1) \|\| (version != wall_clock->version));
133
134	delta = pvclock_clocksource_read(vcpu_time); /* time since system boot */
135	delta += now.tv_sec * (u64)NSEC_PER_SEC + now.tv_nsec;
136
137	now.tv_nsec = do_div(delta, NSEC_PER_SEC);
138	now.tv_sec = delta;
139
140	set_normalized_timespec(ts, now.tv_sec, now.tv_nsec);
141	}