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/* $OpenBSD: pvclock.c,v 1.10 2024/05/14 08:26:13 jsg Exp $ */
/*
* Copyright (c) 2018 Reyk Floeter <reyk@openbsd.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#if !defined(__i386__) && !defined(__amd64__)
#error pvclock(4) is only supported on i386 and amd64
#endif
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/timetc.h>
#include <sys/timeout.h>
#include <sys/malloc.h>
#include <sys/atomic.h>
#include <machine/cpu.h>
#include <machine/atomic.h>
#include <uvm/uvm_extern.h>
#include <dev/pv/pvvar.h>
#include <dev/pv/pvreg.h>
uint pvclock_lastcount;
struct pvclock_softc {
struct device sc_dev;
void *sc_time;
paddr_t sc_paddr;
struct timecounter *sc_tc;
};
#define DEVNAME(_s) ((_s)->sc_dev.dv_xname)
int pvclock_match(struct device *, void *, void *);
void pvclock_attach(struct device *, struct device *, void *);
int pvclock_activate(struct device *, int);
uint pvclock_get_timecount(struct timecounter *);
static inline uint32_t
pvclock_read_begin(const struct pvclock_time_info *);
static inline int
pvclock_read_done(const struct pvclock_time_info *, uint32_t);
const struct cfattach pvclock_ca = {
sizeof(struct pvclock_softc),
pvclock_match,
pvclock_attach,
NULL,
pvclock_activate
};
struct cfdriver pvclock_cd = {
NULL,
"pvclock",
DV_DULL
};
struct timecounter pvclock_timecounter = {
.tc_get_timecount = pvclock_get_timecount,
.tc_counter_mask = ~0u,
.tc_frequency = 0,
.tc_name = NULL,
.tc_quality = -2000,
.tc_priv = NULL,
.tc_user = 0,
};
int
pvclock_match(struct device *parent, void *match, void *aux)
{
struct pv_attach_args *pva = aux;
struct pvbus_hv *hv;
/*
* pvclock is provided by different hypervisors, we currently
* only support the "kvmclock".
*/
hv = &pva->pva_hv[PVBUS_KVM];
if (hv->hv_base == 0)
hv = &pva->pva_hv[PVBUS_OPENBSD];
if (hv->hv_base != 0) {
/*
* We only implement support for the 2nd version of pvclock.
* The first version is basically the same but with different
* non-standard MSRs and it is deprecated.
*/
if ((hv->hv_features & (1 << KVM_FEATURE_CLOCKSOURCE2)) == 0)
return (0);
/*
* Only the "stable" clock with a sync'ed TSC is supported.
* In this case the host guarantees that the TSC is constant
* and invariant, either by the underlying TSC or by passing
* on a synchronized value.
*/
if ((hv->hv_features &
(1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT)) == 0)
return (0);
return (1);
}
return (0);
}
void
pvclock_attach(struct device *parent, struct device *self, void *aux)
{
struct pvclock_softc *sc = (struct pvclock_softc *)self;
struct pvclock_time_info *ti;
paddr_t pa;
uint32_t version;
uint8_t flags;
if ((sc->sc_time = km_alloc(PAGE_SIZE,
&kv_any, &kp_zero, &kd_nowait)) == NULL) {
printf(": time page allocation failed\n");
return;
}
if (!pmap_extract(pmap_kernel(), (vaddr_t)sc->sc_time, &pa)) {
printf(": time page PA extraction failed\n");
km_free(sc->sc_time, PAGE_SIZE, &kv_any, &kp_zero);
return;
}
wrmsr(KVM_MSR_SYSTEM_TIME, pa | PVCLOCK_SYSTEM_TIME_ENABLE);
sc->sc_paddr = pa;
ti = sc->sc_time;
do {
version = pvclock_read_begin(ti);
flags = ti->ti_flags;
} while (!pvclock_read_done(ti, version));
sc->sc_tc = &pvclock_timecounter;
sc->sc_tc->tc_name = DEVNAME(sc);
sc->sc_tc->tc_frequency = 1000000000ULL;
sc->sc_tc->tc_priv = sc;
pvclock_lastcount = 0;
/* Better than HPET but below TSC */
sc->sc_tc->tc_quality = 1500;
if ((flags & PVCLOCK_FLAG_TSC_STABLE) == 0) {
/* if tsc is not stable, set a lower priority */
/* Better than i8254 but below HPET */
sc->sc_tc->tc_quality = 500;
}
tc_init(sc->sc_tc);
printf("\n");
}
int
pvclock_activate(struct device *self, int act)
{
struct pvclock_softc *sc = (struct pvclock_softc *)self;
int rv = 0;
paddr_t pa = sc->sc_paddr;
switch (act) {
case DVACT_POWERDOWN:
wrmsr(KVM_MSR_SYSTEM_TIME, pa & ~PVCLOCK_SYSTEM_TIME_ENABLE);
break;
case DVACT_RESUME:
wrmsr(KVM_MSR_SYSTEM_TIME, pa | PVCLOCK_SYSTEM_TIME_ENABLE);
break;
}
return (rv);
}
static inline uint32_t
pvclock_read_begin(const struct pvclock_time_info *ti)
{
uint32_t version = ti->ti_version & ~0x1;
virtio_membar_sync();
return (version);
}
static inline int
pvclock_read_done(const struct pvclock_time_info *ti,
uint32_t version)
{
virtio_membar_sync();
return (ti->ti_version == version);
}
uint
pvclock_get_timecount(struct timecounter *tc)
{
struct pvclock_softc *sc = tc->tc_priv;
struct pvclock_time_info *ti;
uint64_t tsc_timestamp, system_time, delta, ctr;
uint32_t version, mul_frac;
int8_t shift;
uint8_t flags;
ti = sc->sc_time;
do {
version = pvclock_read_begin(ti);
system_time = ti->ti_system_time;
tsc_timestamp = ti->ti_tsc_timestamp;
mul_frac = ti->ti_tsc_to_system_mul;
shift = ti->ti_tsc_shift;
flags = ti->ti_flags;
} while (!pvclock_read_done(ti, version));
/*
* The algorithm is described in
* linux/Documentation/virtual/kvm/msr.txt
*/
delta = rdtsc() - tsc_timestamp;
if (shift < 0)
delta >>= -shift;
else
delta <<= shift;
ctr = ((delta * mul_frac) >> 32) + system_time;
if ((flags & PVCLOCK_FLAG_TSC_STABLE) != 0)
return (ctr);
if (ctr < pvclock_lastcount)
return (pvclock_lastcount);
atomic_swap_uint(&pvclock_lastcount, ctr);
return (ctr);
}
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