forked from Minki/linux
7af192c954
This patch adds structs for the paravirt clocksource ABI used by both xen and kvm (pvclock-abi.h). It also adds some helper functions to read system time and wall clock time from a paravirtual clocksource (pvclock.[ch]). They are based on the xen code. They are enabled using CONFIG_PARAVIRT_CLOCK. Subsequent patches of this series will put the code in use. Signed-off-by: Gerd Hoffmann <kraxel@redhat.com> Acked-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
142 lines
3.8 KiB
C
142 lines
3.8 KiB
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);
|
|
}
|