[PATCH v2 0/2] clocksource/hyperv: Miscellaneous changes

[PATCH v2 0/2] clocksource/hyperv: Miscellaneous changes

[Andrea Parri]

Provide some refactoring and adjustments to the Hyper-V clocksources
code.

Changes since v1 [1]:
  - Rebased on Daniel's repo/branch
  - Added Reviewed-by: tags

[1] https://lkml.kernel.org/r/20191210093054.32230-1-parri.andrea@gmail.com

Andrea Parri (2):
  clocksource/hyperv: Untangle stimers and timesync from clocksources
  clocksource/hyperv: Set TSC clocksource as default w/ InvariantTSC

 drivers/clocksource/hyperv_timer.c | 48 ++++++++++++++++++++----------
 drivers/hv/hv_util.c               |  8 ++---
 include/clocksource/hyperv_timer.h |  2 +-
 3 files changed, 38 insertions(+), 20 deletions(-)

-- 
2.24.0

[PATCH v2 1/2] clocksource/hyperv: Untangle stimers and timesync from clocksources

[Andrea Parri]

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

[PATCH v2 2/2] clocksource/hyperv: Set TSC clocksource as default w/ InvariantTSC

[Andrea Parri]

Change the Hyper-V clocksource ratings to 250, below the TSC clocksource
rating of 300.  In configurations where Hyper-V offers an InvariantTSC,
the TSC is not marked "unstable", so the TSC clocksource is available
and preferred.  With the higher rating, it will be the default.  On
older hardware and Hyper-V versions, the TSC is marked "unstable", so no
TSC clocksource is created and the selected Hyper-V clocksource will be
the default.

Signed-off-by: Andrea Parri <parri.andrea@gmail.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
---
 drivers/clocksource/hyperv_timer.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
index be98d201d585d..3881c2bf987e4 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -208,6 +208,14 @@ EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup);
  * the other that uses the TSC reference page feature as defined in the
  * TLFS.  The MSR version is for compatibility with old versions of
  * Hyper-V and 32-bit x86.  The TSC reference page version is preferred.
+ *
+ * The Hyper-V clocksource ratings of 250 are chosen to be below the
+ * TSC clocksource rating of 300.  In configurations where Hyper-V offers
+ * an InvariantTSC, the TSC is not marked "unstable", so the TSC clocksource
+ * is available and preferred.  With the higher rating, it will be the
+ * default.  On older hardware and Hyper-V versions, the TSC is marked
+ * "unstable", so no TSC clocksource is created and the selected Hyper-V
+ * clocksource will be the default.
  */
 
 u64 (*hv_read_reference_counter)(void);
@@ -269,7 +277,7 @@ static void resume_hv_clock_tsc(struct clocksource *arg)
 
 static struct clocksource hyperv_cs_tsc = {
 	.name	= "hyperv_clocksource_tsc_page",
-	.rating	= 400,
+	.rating	= 250,
 	.read	= read_hv_clock_tsc_cs,
 	.mask	= CLOCKSOURCE_MASK(64),
 	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
@@ -301,7 +309,7 @@ static u64 read_hv_sched_clock_msr(void)
 
 static struct clocksource hyperv_cs_msr = {
 	.name	= "hyperv_clocksource_msr",
-	.rating	= 400,
+	.rating	= 250,
 	.read	= read_hv_clock_msr_cs,
 	.mask	= CLOCKSOURCE_MASK(64),
 	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
-- 
2.24.0

Re: [PATCH v2 0/2] clocksource/hyperv: Miscellaneous changes

[Daniel Lezcano]

On 09/01/2020 17:06, Andrea Parri wrote:
> Provide some refactoring and adjustments to the Hyper-V clocksources
> code.
> 
> Changes since v1 [1]:
>   - Rebased on Daniel's repo/branch
>   - Added Reviewed-by: tags
> 
> [1] https://lkml.kernel.org/r/20191210093054.32230-1-parri.andrea@gmail.com
> 
> Andrea Parri (2):
>   clocksource/hyperv: Untangle stimers and timesync from clocksources
>   clocksource/hyperv: Set TSC clocksource as default w/ InvariantTSC
> 
>  drivers/clocksource/hyperv_timer.c | 48 ++++++++++++++++++++----------
>  drivers/hv/hv_util.c               |  8 ++---
>  include/clocksource/hyperv_timer.h |  2 +-
>  3 files changed, 38 insertions(+), 20 deletions(-)

Applied, thanks.


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