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Subject[PATCH v2 1/2] clocksource/hyperv: Untangle stimers and timesync from clocksources
Date
hyperv_timer.c exports hyperv_cs, which is used by stimers and the
timesync mechanism. However, the clocksource dependency is not
needed: these mechanisms only depend on the partition reference
counter (which can be read via a MSR or via the TSC Reference Page).

Introduce the (function) pointer hv_read_reference_counter, as an
embodiment of the partition reference counter read, and export it
in place of the hyperv_cs pointer. The latter can be removed.

This should clarify that there's no relationship between Hyper-V
stimers & timesync and the Linux clocksource abstractions. No
functional or semantic change.

Suggested-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Andrea Parri <parri.andrea@gmail.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
---
drivers/clocksource/hyperv_timer.c | 36 +++++++++++++++++++-----------
drivers/hv/hv_util.c | 8 +++----
include/clocksource/hyperv_timer.h | 2 +-
3 files changed, 28 insertions(+), 18 deletions(-)

diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
index 51ff43274db7b..be98d201d585d 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -56,7 +56,7 @@ static int hv_ce_set_next_event(unsigned long delta,
{
u64 current_tick;

- current_tick = hyperv_cs->read(NULL);
+ current_tick = hv_read_reference_counter();
current_tick += delta;
hv_init_timer(0, current_tick);
return 0;
@@ -210,8 +210,8 @@ EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup);
* Hyper-V and 32-bit x86. The TSC reference page version is preferred.
*/

-struct clocksource *hyperv_cs;
-EXPORT_SYMBOL_GPL(hyperv_cs);
+u64 (*hv_read_reference_counter)(void);
+EXPORT_SYMBOL_GPL(hv_read_reference_counter);

static union {
struct ms_hyperv_tsc_page page;
@@ -224,7 +224,7 @@ struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
}
EXPORT_SYMBOL_GPL(hv_get_tsc_page);

-static u64 notrace read_hv_clock_tsc(struct clocksource *arg)
+static u64 notrace read_hv_clock_tsc(void)
{
u64 current_tick = hv_read_tsc_page(hv_get_tsc_page());

@@ -234,9 +234,14 @@ static u64 notrace read_hv_clock_tsc(struct clocksource *arg)
return current_tick;
}

+static u64 notrace read_hv_clock_tsc_cs(struct clocksource *arg)
+{
+ return read_hv_clock_tsc();
+}
+
static u64 read_hv_sched_clock_tsc(void)
{
- return read_hv_clock_tsc(NULL) - hv_sched_clock_offset;
+ return read_hv_clock_tsc() - hv_sched_clock_offset;
}

static void suspend_hv_clock_tsc(struct clocksource *arg)
@@ -265,14 +270,14 @@ static void resume_hv_clock_tsc(struct clocksource *arg)
static struct clocksource hyperv_cs_tsc = {
.name = "hyperv_clocksource_tsc_page",
.rating = 400,
- .read = read_hv_clock_tsc,
+ .read = read_hv_clock_tsc_cs,
.mask = CLOCKSOURCE_MASK(64),
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
.suspend= suspend_hv_clock_tsc,
.resume = resume_hv_clock_tsc,
};

-static u64 notrace read_hv_clock_msr(struct clocksource *arg)
+static u64 notrace read_hv_clock_msr(void)
{
u64 current_tick;
/*
@@ -284,15 +289,20 @@ static u64 notrace read_hv_clock_msr(struct clocksource *arg)
return current_tick;
}

+static u64 notrace read_hv_clock_msr_cs(struct clocksource *arg)
+{
+ return read_hv_clock_msr();
+}
+
static u64 read_hv_sched_clock_msr(void)
{
- return read_hv_clock_msr(NULL) - hv_sched_clock_offset;
+ return read_hv_clock_msr() - hv_sched_clock_offset;
}

static struct clocksource hyperv_cs_msr = {
.name = "hyperv_clocksource_msr",
.rating = 400,
- .read = read_hv_clock_msr,
+ .read = read_hv_clock_msr_cs,
.mask = CLOCKSOURCE_MASK(64),
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
@@ -305,7 +315,7 @@ static bool __init hv_init_tsc_clocksource(void)
if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))
return false;

- hyperv_cs = &hyperv_cs_tsc;
+ hv_read_reference_counter = read_hv_clock_tsc;
phys_addr = virt_to_phys(hv_get_tsc_page());

/*
@@ -323,7 +333,7 @@ static bool __init hv_init_tsc_clocksource(void)
hv_set_clocksource_vdso(hyperv_cs_tsc);
clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);

- hv_sched_clock_offset = hyperv_cs->read(hyperv_cs);
+ hv_sched_clock_offset = hv_read_reference_counter();
hv_setup_sched_clock(read_hv_sched_clock_tsc);

return true;
@@ -345,10 +355,10 @@ void __init hv_init_clocksource(void)
if (!(ms_hyperv.features & HV_MSR_TIME_REF_COUNT_AVAILABLE))
return;

- hyperv_cs = &hyperv_cs_msr;
+ hv_read_reference_counter = read_hv_clock_msr;
clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);

- hv_sched_clock_offset = hyperv_cs->read(hyperv_cs);
+ hv_sched_clock_offset = hv_read_reference_counter();
hv_setup_sched_clock(read_hv_sched_clock_msr);
}
EXPORT_SYMBOL_GPL(hv_init_clocksource);
diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c
index e32681ee7b9f6..ef338db3d3599 100644
--- a/drivers/hv/hv_util.c
+++ b/drivers/hv/hv_util.c
@@ -211,7 +211,7 @@ static struct timespec64 hv_get_adj_host_time(void)
unsigned long flags;

spin_lock_irqsave(&host_ts.lock, flags);
- reftime = hyperv_cs->read(hyperv_cs);
+ reftime = hv_read_reference_counter();
newtime = host_ts.host_time + (reftime - host_ts.ref_time);
ts = ns_to_timespec64((newtime - WLTIMEDELTA) * 100);
spin_unlock_irqrestore(&host_ts.lock, flags);
@@ -250,7 +250,7 @@ static inline void adj_guesttime(u64 hosttime, u64 reftime, u8 adj_flags)
*/
spin_lock_irqsave(&host_ts.lock, flags);

- cur_reftime = hyperv_cs->read(hyperv_cs);
+ cur_reftime = hv_read_reference_counter();
host_ts.host_time = hosttime;
host_ts.ref_time = cur_reftime;

@@ -315,7 +315,7 @@ static void timesync_onchannelcallback(void *context)
sizeof(struct vmbuspipe_hdr) +
sizeof(struct icmsg_hdr)];
adj_guesttime(timedatap->parenttime,
- hyperv_cs->read(hyperv_cs),
+ hv_read_reference_counter(),
timedatap->flags);
}
}
@@ -523,7 +523,7 @@ static struct ptp_clock *hv_ptp_clock;
static int hv_timesync_init(struct hv_util_service *srv)
{
/* TimeSync requires Hyper-V clocksource. */
- if (!hyperv_cs)
+ if (!hv_read_reference_counter)
return -ENODEV;

spin_lock_init(&host_ts.lock);
diff --git a/include/clocksource/hyperv_timer.h b/include/clocksource/hyperv_timer.h
index 422f5e5237be4..373a3ece88121 100644
--- a/include/clocksource/hyperv_timer.h
+++ b/include/clocksource/hyperv_timer.h
@@ -29,7 +29,7 @@ extern void hv_stimer_global_cleanup(void);
extern void hv_stimer0_isr(void);

#ifdef CONFIG_HYPERV_TIMER
-extern struct clocksource *hyperv_cs;
+extern u64 (*hv_read_reference_counter)(void);
extern void hv_init_clocksource(void);

extern struct ms_hyperv_tsc_page *hv_get_tsc_page(void);
--
2.24.0
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