clocksource/drivers/hyper-v: Untangle stimers and timesync from clocksources

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>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200109160650.16150-2-parri.andrea@gmail.com

diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
index 12d75b50a3178e6332512a94fb5f7ae5c61074e4..42748adccc98c3f372423fb2b06c6a74e0a2d3fb 100644 (file)
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -66,7 +66,7 @@ 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;
@@ -304,8 +304,8 @@ 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;
@@ -318,7 +318,7 @@ 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());
 
@@ -328,9 +328,14 @@ 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)
@@ -359,14 +364,14 @@ 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;
        /*
@@ -378,15 +383,20 @@ 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,
 };
@@ -399,7 +409,7 @@ 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());
 
        /*
@@ -417,7 +427,7 @@ 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;
@@ -439,10 +449,10 @@ 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 766bd84573461a58d5c4d6dc52fec876502c050b..296f9098c9e4624a38d0382c3266a94af26a02eb 100644 (file)
--- 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);
                        }
                }
@@ -524,7 +524,7 @@ 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 553e539469f04cb74db1b36a213dec794fad10b2..34eef083c9882fafbd3bf5cc25a0dd5fdb38b06d 100644 (file)
--- a/include/clocksource/hyperv_timer.h
+++ b/include/clocksource/hyperv_timer.h
@@ -30,7 +30,7 @@ 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);