[PATCH v3 0/2] Drivers: hv: Move Hyper-V clock/timer code to separate clocksource driver

[PATCH v3 0/2] Drivers: hv: Move Hyper-V clock/timer code to separate clocksource driver

[Michael Kelley]

This patch series moves Hyper-V clock/timer code to a separate Hyper-V
clocksource driver. Previously, Hyper-V clock/timer code and data
structures were mixed in with other Hyper-V code in the ISA independent
drivers/hv code as well as in arch dependent code. The new Hyper-V
clocksource driver is ISA independent, with a just few dependencies on
arch specific functions. The patch series does not change any behavior
or functionality -- it only reorganizes the existing code and fixes up
the linkages. A few places outside of Hyper-V code are fixed up to use
the new #include file structure.

This restructuring is in response to Marc Zyngier's review comments
on supporting Hyper-V running on ARM64, and is a good idea in general.
It increases the amount of code shared between the x86 and ARM64
architectures, and reduces the size of the new code for supporting
Hyper-V on ARM64. A new version of the Hyper-V on ARM64 patches will
follow once this clocksource restructuring is accepted.

The code is diff'ed against Linux 5.2.0-rc1-next-20190524.

Changes in v3:
* Removed boolean argument to hv_init_clocksource(). Always call
sched_clock_register, which is needed on ARM64 but a no-op on x86.
* Removed separate cpuhp setup in hv_stimer_alloc() and instead
directly call hv_stimer_init() and hv_stimer_cleanup() from
corresponding VMbus functions.  This more closely matches original
code and avoids clocksource stop/restart problems on ARM64 when
VMbus code denies CPU offlining request.

Changes in v2:
* Revised commit short descriptions so the distinction between
the first and second patches is clearer [GregKH]
* Renamed new clocksource driver files and functions to use
existing "timer" and "stimer" names instead of introducing
"syntimer". [Vitaly Kuznetsov]
* Introduced CONFIG_HYPER_TIMER to fix build problem when
CONFIG_HYPERV=m [Vitaly Kuznetsov]
* Added "Suggested-by: Marc Zyngier"

Michael Kelley (2):
  Drivers: hv: Create Hyper-V clocksource driver from existing
    clockevents code
  Drivers: hv: Move Hyper-V clocksource code to new clocksource driver

 MAINTAINERS                          |   2 +
 arch/x86/entry/vdso/vclock_gettime.c |   1 +
 arch/x86/entry/vdso/vma.c            |   2 +-
 arch/x86/hyperv/hv_init.c            |  91 +---------
 arch/x86/include/asm/hyperv-tlfs.h   |   6 +
 arch/x86/include/asm/mshyperv.h      |  81 ++-------
 arch/x86/kernel/cpu/mshyperv.c       |   2 +
 arch/x86/kvm/x86.c                   |   1 +
 drivers/clocksource/Makefile         |   1 +
 drivers/clocksource/hyperv_timer.c   | 321 +++++++++++++++++++++++++++++++++++
 drivers/hv/Kconfig                   |   3 +
 drivers/hv/hv.c                      | 156 +----------------
 drivers/hv/hv_util.c                 |   1 +
 drivers/hv/hyperv_vmbus.h            |   3 -
 drivers/hv/vmbus_drv.c               |  42 ++---
 include/clocksource/hyperv_timer.h   | 105 ++++++++++++
 16 files changed, 484 insertions(+), 334 deletions(-)
 create mode 100644 drivers/clocksource/hyperv_timer.c
 create mode 100644 include/clocksource/hyperv_timer.h

-- 
1.8.3.1

[PATCH v3 1/2] Drivers: hv: Create Hyper-V clocksource driver from existing clockevents code

[Michael Kelley]

Clockevents code for Hyper-V synthetic timers is currently mixed
in with other Hyper-V code. Move the code to a Hyper-V specific
driver in the "clocksource" directory. Update the VMbus driver
to call initialization and cleanup routines since the Hyper-V
synthetic timers are not independently enumerated in ACPI.

No behavior is changed and no new functionality is added.

Suggested-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Michael Kelley <mikelley@microsoft.com>
---
 MAINTAINERS                        |   2 +
 arch/x86/include/asm/hyperv-tlfs.h |   6 ++
 arch/x86/kernel/cpu/mshyperv.c     |   2 +
 drivers/clocksource/Makefile       |   1 +
 drivers/clocksource/hyperv_timer.c | 191 +++++++++++++++++++++++++++++++++++++
 drivers/hv/Kconfig                 |   3 +
 drivers/hv/hv.c                    | 156 +-----------------------------
 drivers/hv/hyperv_vmbus.h          |   3 -
 drivers/hv/vmbus_drv.c             |  42 ++++----
 include/clocksource/hyperv_timer.h |  27 ++++++
 10 files changed, 258 insertions(+), 175 deletions(-)
 create mode 100644 drivers/clocksource/hyperv_timer.c
 create mode 100644 include/clocksource/hyperv_timer.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 992f1dd..cf2a5b7 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7294,6 +7294,7 @@ F:	arch/x86/include/asm/trace/hyperv.h
 F:	arch/x86/include/asm/hyperv-tlfs.h
 F:	arch/x86/kernel/cpu/mshyperv.c
 F:	arch/x86/hyperv
+F:	drivers/clocksource/hyperv_timer.c
 F:	drivers/hid/hid-hyperv.c
 F:	drivers/hv/
 F:	drivers/input/serio/hyperv-keyboard.c
@@ -7304,6 +7305,7 @@ F:	drivers/uio/uio_hv_generic.c
 F:	drivers/video/fbdev/hyperv_fb.c
 F:	drivers/iommu/hyperv_iommu.c
 F:	net/vmw_vsock/hyperv_transport.c
+F:	include/clocksource/hyperv_timer.h
 F:	include/linux/hyperv.h
 F:	include/uapi/linux/hyperv.h
 F:	tools/hv/
diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
index cdf44aa..af78cd7 100644
--- a/arch/x86/include/asm/hyperv-tlfs.h
+++ b/arch/x86/include/asm/hyperv-tlfs.h
@@ -401,6 +401,12 @@ enum HV_GENERIC_SET_FORMAT {
 #define HV_STATUS_INVALID_CONNECTION_ID		18
 #define HV_STATUS_INSUFFICIENT_BUFFERS		19
 
+/*
+ * The Hyper-V TimeRefCount register and the TSC
+ * page provide a guest VM clock with 100ns tick rate
+ */
+#define HV_CLOCK_HZ (NSEC_PER_SEC/100)
+
 typedef struct _HV_REFERENCE_TSC_PAGE {
 	__u32 tsc_sequence;
 	__u32 res1;
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index faae611..b18ede4 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -21,6 +21,7 @@
 #include <linux/irq.h>
 #include <linux/kexec.h>
 #include <linux/i8253.h>
+#include <linux/random.h>
 #include <asm/processor.h>
 #include <asm/hypervisor.h>
 #include <asm/hyperv-tlfs.h>
@@ -84,6 +85,7 @@ __visible void __irq_entry hv_stimer0_vector_handler(struct pt_regs *regs)
 	inc_irq_stat(hyperv_stimer0_count);
 	if (hv_stimer0_handler)
 		hv_stimer0_handler();
+	add_interrupt_randomness(HYPERV_STIMER0_VECTOR, 0);
 	ack_APIC_irq();
 
 	exiting_irq();
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index 236858f..2b65c5f 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -84,3 +84,4 @@ obj-$(CONFIG_ATCPIT100_TIMER)		+= timer-atcpit100.o
 obj-$(CONFIG_RISCV_TIMER)		+= timer-riscv.o
 obj-$(CONFIG_CSKY_MP_TIMER)		+= timer-mp-csky.o
 obj-$(CONFIG_GX6605S_TIMER)		+= timer-gx6605s.o
+obj-$(CONFIG_HYPERV_TIMER)		+= hyperv_timer.o
diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
new file mode 100644
index 0000000..30615f3
--- /dev/null
+++ b/drivers/clocksource/hyperv_timer.c
@@ -0,0 +1,191 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Clocksource driver for the synthetic counter and timers
+ * provided by the Hyper-V hypervisor to guest VMs, as described
+ * in the Hyper-V Top Level Functional Spec (TLFS). This driver
+ * is instruction set architecture independent.
+ *
+ * Copyright (C) 2019, Microsoft, Inc.
+ *
+ * Author:  Michael Kelley <mikelley@microsoft.com>
+ */
+
+#include <linux/percpu.h>
+#include <linux/cpumask.h>
+#include <linux/clockchips.h>
+#include <linux/mm.h>
+#include <clocksource/hyperv_timer.h>
+#include <asm/hyperv-tlfs.h>
+#include <asm/mshyperv.h>
+
+static struct clock_event_device __percpu *hv_clock_event;
+
+/*
+ * If false, we're using the old mechanism for stimer0 interrupts
+ * where it sends a VMbus message when it expires. The old
+ * mechanism is used when running on older versions of Hyper-V
+ * that don't support Direct Mode. While Hyper-V provides
+ * four stimer's per CPU, Linux uses only stimer0.
+ */
+static bool direct_mode_enabled;
+
+static int stimer0_irq;
+static int stimer0_vector;
+static int stimer0_message_sint;
+
+/*
+ * ISR for when stimer0 is operating in Direct Mode.  Direct Mode
+ * does not use VMbus or any VMbus messages, so process here and not
+ * in the VMbus driver code.
+ */
+void hv_stimer0_isr(void)
+{
+	struct clock_event_device *ce;
+
+	ce = this_cpu_ptr(hv_clock_event);
+	ce->event_handler(ce);
+}
+EXPORT_SYMBOL_GPL(hv_stimer0_isr);
+
+static int hv_ce_set_next_event(unsigned long delta,
+				struct clock_event_device *evt)
+{
+	u64 current_tick;
+
+	WARN_ON(!clockevent_state_oneshot(evt));
+
+	current_tick = hyperv_cs->read(NULL);
+	current_tick += delta;
+	hv_init_timer(0, current_tick);
+	return 0;
+}
+
+static int hv_ce_shutdown(struct clock_event_device *evt)
+{
+	hv_init_timer(0, 0);
+	hv_init_timer_config(0, 0);
+	if (direct_mode_enabled)
+		hv_disable_stimer0_percpu_irq(stimer0_irq);
+
+	return 0;
+}
+
+static int hv_ce_set_oneshot(struct clock_event_device *evt)
+{
+	union hv_stimer_config timer_cfg;
+
+	timer_cfg.as_uint64 = 0;
+	timer_cfg.enable = 1;
+	timer_cfg.auto_enable = 1;
+	if (direct_mode_enabled) {
+		/*
+		 * When it expires, the timer will directly interrupt
+		 * on the specified hardware vector/IRQ.
+		 */
+		timer_cfg.direct_mode = 1;
+		timer_cfg.apic_vector = stimer0_vector;
+		hv_enable_stimer0_percpu_irq(stimer0_irq);
+	} else {
+		/*
+		 * When it expires, the timer will generate a VMbus message,
+		 * to be handled by the normal VMbus interrupt handler.
+		 */
+		timer_cfg.direct_mode = 0;
+		timer_cfg.sintx = stimer0_message_sint;
+	}
+	hv_init_timer_config(0, timer_cfg.as_uint64);
+	return 0;
+}
+
+/*
+ * hv_stimer_init - Per-cpu initialization of the clockevent
+ */
+int hv_stimer_init(unsigned int cpu)
+{
+	struct clock_event_device *ce;
+
+	if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE) {
+		ce = per_cpu_ptr(hv_clock_event, cpu);
+		ce->name = "Hyper-V clockevent";
+		ce->features = CLOCK_EVT_FEAT_ONESHOT;
+		ce->cpumask = cpumask_of(cpu);
+		ce->rating = 1000;
+		ce->set_state_shutdown = hv_ce_shutdown;
+		ce->set_state_oneshot = hv_ce_set_oneshot;
+		ce->set_next_event = hv_ce_set_next_event;
+
+		clockevents_config_and_register(ce,
+						HV_CLOCK_HZ,
+						HV_MIN_DELTA_TICKS,
+						HV_MAX_MAX_DELTA_TICKS);
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(hv_stimer_init);
+
+/*
+ * hv_stimer_cleanup - Per-cpu cleanup of the clockevent
+ */
+int hv_stimer_cleanup(unsigned int cpu)
+{
+	struct clock_event_device *ce;
+
+	/* Turn off clockevent device */
+	if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE) {
+		ce = per_cpu_ptr(hv_clock_event, cpu);
+		clockevents_unbind_device(ce, cpu);
+		hv_ce_shutdown(ce);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(hv_stimer_cleanup);
+
+/* hv_stimer_alloc - Global initialization of the clockevent and stimer0 */
+int hv_stimer_alloc(int sint)
+{
+	hv_clock_event = alloc_percpu(struct clock_event_device);
+	if (!hv_clock_event)
+		return -ENOMEM;
+
+	direct_mode_enabled = ms_hyperv.misc_features &
+			HV_STIMER_DIRECT_MODE_AVAILABLE;
+	if (direct_mode_enabled &&
+	    hv_setup_stimer0_irq(&stimer0_irq, &stimer0_vector,
+				hv_stimer0_isr)) {
+		free_percpu(hv_clock_event);
+		return -EINVAL;
+	}
+
+	stimer0_message_sint = sint;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(hv_stimer_alloc);
+
+/* hv_stimer_free - Free global resources allocated by hv_stimer_alloc() */
+void hv_stimer_free(void)
+{
+	if (direct_mode_enabled)
+		hv_remove_stimer0_irq(stimer0_irq);
+	free_percpu(hv_clock_event);
+}
+EXPORT_SYMBOL_GPL(hv_stimer_free);
+
+/*
+ * Do a global cleanup of clockevents for the cases of kexec and
+ * vmbus exit
+ */
+void hv_stimer_global_cleanup(void)
+{
+	int	cpu;
+	struct clock_event_device *ce;
+
+	if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE)
+		for_each_present_cpu(cpu) {
+			ce = per_cpu_ptr(hv_clock_event, cpu);
+			clockevents_unbind_device(ce, cpu);
+		}
+	hv_stimer_free();
+}
+EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup);
diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
index 1c1a251..c423e57 100644
--- a/drivers/hv/Kconfig
+++ b/drivers/hv/Kconfig
@@ -10,6 +10,9 @@ config HYPERV
 	  Select this option to run Linux as a Hyper-V client operating
 	  system.
 
+config HYPERV_TIMER
+	def_bool HYPERV
+
 config HYPERV_TSCPAGE
        def_bool HYPERV && X86_64
 
diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
index 4565302..bd6452f 100644
--- a/drivers/hv/hv.c
+++ b/drivers/hv/hv.c
@@ -29,6 +29,7 @@
 #include <linux/version.h>
 #include <linux/random.h>
 #include <linux/clockchips.h>
+#include <clocksource/hyperv_timer.h>
 #include <asm/mshyperv.h>
 #include "hyperv_vmbus.h"
 
@@ -36,21 +37,6 @@
 struct hv_context hv_context;
 
 /*
- * If false, we're using the old mechanism for stimer0 interrupts
- * where it sends a VMbus message when it expires. The old
- * mechanism is used when running on older versions of Hyper-V
- * that don't support Direct Mode. While Hyper-V provides
- * four stimer's per CPU, Linux uses only stimer0.
- */
-static bool direct_mode_enabled;
-static int stimer0_irq;
-static int stimer0_vector;
-
-#define HV_TIMER_FREQUENCY (10 * 1000 * 1000) /* 100ns period */
-#define HV_MAX_MAX_DELTA_TICKS 0xffffffff
-#define HV_MIN_DELTA_TICKS 1
-
-/*
  * hv_init - Main initialization routine.
  *
  * This routine must be called before any other routines in here are called
@@ -60,9 +46,6 @@ int hv_init(void)
 	hv_context.cpu_context = alloc_percpu(struct hv_per_cpu_context);
 	if (!hv_context.cpu_context)
 		return -ENOMEM;
-
-	direct_mode_enabled = ms_hyperv.misc_features &
-			HV_STIMER_DIRECT_MODE_AVAILABLE;
 	return 0;
 }
 
@@ -101,89 +84,6 @@ int hv_post_message(union hv_connection_id connection_id,
 	return status & 0xFFFF;
 }
 
-/*
- * ISR for when stimer0 is operating in Direct Mode.  Direct Mode
- * does not use VMbus or any VMbus messages, so process here and not
- * in the VMbus driver code.
- */
-
-static void hv_stimer0_isr(void)
-{
-	struct hv_per_cpu_context *hv_cpu;
-
-	hv_cpu = this_cpu_ptr(hv_context.cpu_context);
-	hv_cpu->clk_evt->event_handler(hv_cpu->clk_evt);
-	add_interrupt_randomness(stimer0_vector, 0);
-}
-
-static int hv_ce_set_next_event(unsigned long delta,
-				struct clock_event_device *evt)
-{
-	u64 current_tick;
-
-	WARN_ON(!clockevent_state_oneshot(evt));
-
-	current_tick = hyperv_cs->read(NULL);
-	current_tick += delta;
-	hv_init_timer(0, current_tick);
-	return 0;
-}
-
-static int hv_ce_shutdown(struct clock_event_device *evt)
-{
-	hv_init_timer(0, 0);
-	hv_init_timer_config(0, 0);
-	if (direct_mode_enabled)
-		hv_disable_stimer0_percpu_irq(stimer0_irq);
-
-	return 0;
-}
-
-static int hv_ce_set_oneshot(struct clock_event_device *evt)
-{
-	union hv_stimer_config timer_cfg;
-
-	timer_cfg.as_uint64 = 0;
-	timer_cfg.enable = 1;
-	timer_cfg.auto_enable = 1;
-	if (direct_mode_enabled) {
-		/*
-		 * When it expires, the timer will directly interrupt
-		 * on the specified hardware vector/IRQ.
-		 */
-		timer_cfg.direct_mode = 1;
-		timer_cfg.apic_vector = stimer0_vector;
-		hv_enable_stimer0_percpu_irq(stimer0_irq);
-	} else {
-		/*
-		 * When it expires, the timer will generate a VMbus message,
-		 * to be handled by the normal VMbus interrupt handler.
-		 */
-		timer_cfg.direct_mode = 0;
-		timer_cfg.sintx = VMBUS_MESSAGE_SINT;
-	}
-	hv_init_timer_config(0, timer_cfg.as_uint64);
-	return 0;
-}
-
-static void hv_init_clockevent_device(struct clock_event_device *dev, int cpu)
-{
-	dev->name = "Hyper-V clockevent";
-	dev->features = CLOCK_EVT_FEAT_ONESHOT;
-	dev->cpumask = cpumask_of(cpu);
-	dev->rating = 1000;
-	/*
-	 * Avoid settint dev->owner = THIS_MODULE deliberately as doing so will
-	 * result in clockevents_config_and_register() taking additional
-	 * references to the hv_vmbus module making it impossible to unload.
-	 */
-
-	dev->set_state_shutdown = hv_ce_shutdown;
-	dev->set_state_oneshot = hv_ce_set_oneshot;
-	dev->set_next_event = hv_ce_set_next_event;
-}
-
-
 int hv_synic_alloc(void)
 {
 	int cpu;
@@ -212,14 +112,6 @@ int hv_synic_alloc(void)
 		tasklet_init(&hv_cpu->msg_dpc,
 			     vmbus_on_msg_dpc, (unsigned long) hv_cpu);
 
-		hv_cpu->clk_evt = kzalloc(sizeof(struct clock_event_device),
-					  GFP_KERNEL);
-		if (hv_cpu->clk_evt == NULL) {
-			pr_err("Unable to allocate clock event device\n");
-			goto err;
-		}
-		hv_init_clockevent_device(hv_cpu->clk_evt, cpu);
-
 		hv_cpu->synic_message_page =
 			(void *)get_zeroed_page(GFP_ATOMIC);
 		if (hv_cpu->synic_message_page == NULL) {
@@ -242,11 +134,6 @@ int hv_synic_alloc(void)
 		INIT_LIST_HEAD(&hv_cpu->chan_list);
 	}
 
-	if (direct_mode_enabled &&
-	    hv_setup_stimer0_irq(&stimer0_irq, &stimer0_vector,
-				hv_stimer0_isr))
-		goto err;
-
 	return 0;
 err:
 	/*
@@ -265,7 +152,6 @@ void hv_synic_free(void)
 		struct hv_per_cpu_context *hv_cpu
 			= per_cpu_ptr(hv_context.cpu_context, cpu);
 
-		kfree(hv_cpu->clk_evt);
 		free_page((unsigned long)hv_cpu->synic_event_page);
 		free_page((unsigned long)hv_cpu->synic_message_page);
 		free_page((unsigned long)hv_cpu->post_msg_page);
@@ -324,36 +210,9 @@ int hv_synic_init(unsigned int cpu)
 
 	hv_set_synic_state(sctrl.as_uint64);
 
-	/*
-	 * Register the per-cpu clockevent source.
-	 */
-	if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE)
-		clockevents_config_and_register(hv_cpu->clk_evt,
-						HV_TIMER_FREQUENCY,
-						HV_MIN_DELTA_TICKS,
-						HV_MAX_MAX_DELTA_TICKS);
-	return 0;
-}
-
-/*
- * hv_synic_clockevents_cleanup - Cleanup clockevent devices
- */
-void hv_synic_clockevents_cleanup(void)
-{
-	int cpu;
+	hv_stimer_init(cpu);
 
-	if (!(ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE))
-		return;
-
-	if (direct_mode_enabled)
-		hv_remove_stimer0_irq(stimer0_irq);
-
-	for_each_present_cpu(cpu) {
-		struct hv_per_cpu_context *hv_cpu
-			= per_cpu_ptr(hv_context.cpu_context, cpu);
-
-		clockevents_unbind_device(hv_cpu->clk_evt, cpu);
-	}
+	return 0;
 }
 
 /*
@@ -401,14 +260,7 @@ int hv_synic_cleanup(unsigned int cpu)
 	if (channel_found && vmbus_connection.conn_state == CONNECTED)
 		return -EBUSY;
 
-	/* Turn off clockevent device */
-	if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE) {
-		struct hv_per_cpu_context *hv_cpu
-			= this_cpu_ptr(hv_context.cpu_context);
-
-		clockevents_unbind_device(hv_cpu->clk_evt, cpu);
-		hv_ce_shutdown(hv_cpu->clk_evt);
-	}
+	hv_stimer_cleanup(cpu);
 
 	hv_get_synint_state(VMBUS_MESSAGE_SINT, shared_sint.as_uint64);
 
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index e5467b8..a8f8aee 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -151,7 +151,6 @@ struct hv_per_cpu_context {
 	 * per-cpu list of the channels based on their CPU affinity.
 	 */
 	struct list_head chan_list;
-	struct clock_event_device *clk_evt;
 };
 
 struct hv_context {
@@ -189,8 +188,6 @@ extern int hv_post_message(union hv_connection_id connection_id,
 
 extern int hv_synic_cleanup(unsigned int cpu);
 
-extern void hv_synic_clockevents_cleanup(void);
-
 /* Interface */
 
 void hv_ringbuffer_pre_init(struct vmbus_channel *channel);
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 1cb9408..89aca5d 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -43,6 +43,7 @@
 #include <linux/kdebug.h>
 #include <linux/efi.h>
 #include <linux/random.h>
+#include <clocksource/hyperv_timer.h>
 #include "hyperv_vmbus.h"
 
 struct vmbus_dynid {
@@ -968,17 +969,6 @@ static void vmbus_onmessage_work(struct work_struct *work)
 	kfree(ctx);
 }
 
-static void hv_process_timer_expiration(struct hv_message *msg,
-					struct hv_per_cpu_context *hv_cpu)
-{
-	struct clock_event_device *dev = hv_cpu->clk_evt;
-
-	if (dev->event_handler)
-		dev->event_handler(dev);
-
-	vmbus_signal_eom(msg, HVMSG_TIMER_EXPIRED);
-}
-
 void vmbus_on_msg_dpc(unsigned long data)
 {
 	struct hv_per_cpu_context *hv_cpu = (void *)data;
@@ -1172,9 +1162,10 @@ static void vmbus_isr(void)
 
 	/* Check if there are actual msgs to be processed */
 	if (msg->header.message_type != HVMSG_NONE) {
-		if (msg->header.message_type == HVMSG_TIMER_EXPIRED)
-			hv_process_timer_expiration(msg, hv_cpu);
-		else
+		if (msg->header.message_type == HVMSG_TIMER_EXPIRED) {
+			hv_stimer0_isr();
+			vmbus_signal_eom(msg, HVMSG_TIMER_EXPIRED);
+		} else
 			tasklet_schedule(&hv_cpu->msg_dpc);
 	}
 
@@ -1276,14 +1267,19 @@ static int vmbus_bus_init(void)
 	ret = hv_synic_alloc();
 	if (ret)
 		goto err_alloc;
+
+	ret = hv_stimer_alloc(VMBUS_MESSAGE_SINT);
+	if (ret < 0)
+		goto err_alloc;
+
 	/*
-	 * Initialize the per-cpu interrupt state and
-	 * connect to the host.
+	 * Initialize the per-cpu interrupt state and stimer state.
+	 * Then connect to the host.
 	 */
 	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "hyperv/vmbus:online",
 				hv_synic_init, hv_synic_cleanup);
 	if (ret < 0)
-		goto err_alloc;
+		goto err_cpuhp;
 	hyperv_cpuhp_online = ret;
 
 	ret = vmbus_connect();
@@ -1331,6 +1327,8 @@ static int vmbus_bus_init(void)
 
 err_connect:
 	cpuhp_remove_state(hyperv_cpuhp_online);
+err_cpuhp:
+	hv_stimer_free();
 err_alloc:
 	hv_synic_free();
 	hv_remove_vmbus_irq();
@@ -2077,7 +2075,7 @@ static int vmbus_acpi_add(struct acpi_device *device)
 
 static void hv_kexec_handler(void)
 {
-	hv_synic_clockevents_cleanup();
+	hv_stimer_global_cleanup();
 	vmbus_initiate_unload(false);
 	vmbus_connection.conn_state = DISCONNECTED;
 	/* Make sure conn_state is set as hv_synic_cleanup checks for it */
@@ -2088,6 +2086,8 @@ static void hv_kexec_handler(void)
 
 static void hv_crash_handler(struct pt_regs *regs)
 {
+	int cpu;
+
 	vmbus_initiate_unload(true);
 	/*
 	 * In crash handler we can't schedule synic cleanup for all CPUs,
@@ -2095,7 +2095,9 @@ static void hv_crash_handler(struct pt_regs *regs)
 	 * for kdump.
 	 */
 	vmbus_connection.conn_state = DISCONNECTED;
-	hv_synic_cleanup(smp_processor_id());
+	cpu = smp_processor_id();
+	hv_stimer_cleanup(cpu);
+	hv_synic_cleanup(cpu);
 	hyperv_cleanup();
 };
 
@@ -2144,7 +2146,7 @@ static void __exit vmbus_exit(void)
 	hv_remove_kexec_handler();
 	hv_remove_crash_handler();
 	vmbus_connection.conn_state = DISCONNECTED;
-	hv_synic_clockevents_cleanup();
+	hv_stimer_global_cleanup();
 	vmbus_disconnect();
 	hv_remove_vmbus_irq();
 	for_each_online_cpu(cpu) {
diff --git a/include/clocksource/hyperv_timer.h b/include/clocksource/hyperv_timer.h
new file mode 100644
index 0000000..ba5dc17
--- /dev/null
+++ b/include/clocksource/hyperv_timer.h
@@ -0,0 +1,27 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * Definitions for the clocksource provided by the Hyper-V
+ * hypervisor to guest VMs, as described in the Hyper-V Top
+ * Level Functional Spec (TLFS).
+ *
+ * Copyright (C) 2019, Microsoft, Inc.
+ *
+ * Author:  Michael Kelley <mikelley@microsoft.com>
+ */
+
+#ifndef __CLKSOURCE_HYPERV_TIMER_H
+#define __CLKSOURCE_HYPERV_TIMER_H
+
+#define HV_MAX_MAX_DELTA_TICKS 0xffffffff
+#define HV_MIN_DELTA_TICKS 1
+
+/* Routines called by the VMbus driver */
+extern int hv_stimer_alloc(int sint);
+extern void hv_stimer_free(void);
+extern int hv_stimer_init(unsigned int cpu);
+extern int hv_stimer_cleanup(unsigned int cpu);
+extern void hv_stimer_global_cleanup(void);
+extern void hv_stimer0_isr(void);
+
+#endif
-- 
1.8.3.1

Re: [PATCH v3 1/2] Drivers: hv: Create Hyper-V clocksource driver from existing clockevents code

[Vitaly Kuznetsov]

Michael Kelley <mikelley@microsoft.com> writes:

> Clockevents code for Hyper-V synthetic timers is currently mixed
> in with other Hyper-V code. Move the code to a Hyper-V specific
> driver in the "clocksource" directory. Update the VMbus driver
> to call initialization and cleanup routines since the Hyper-V
> synthetic timers are not independently enumerated in ACPI.
>
> No behavior is changed and no new functionality is added.
>
> Suggested-by: Marc Zyngier <marc.zyngier@arm.com>
> Signed-off-by: Michael Kelley <mikelley@microsoft.com>
> ---
>  MAINTAINERS                        |   2 +
>  arch/x86/include/asm/hyperv-tlfs.h |   6 ++
>  arch/x86/kernel/cpu/mshyperv.c     |   2 +
>  drivers/clocksource/Makefile       |   1 +
>  drivers/clocksource/hyperv_timer.c | 191 +++++++++++++++++++++++++++++++++++++
>  drivers/hv/Kconfig                 |   3 +
>  drivers/hv/hv.c                    | 156 +-----------------------------
>  drivers/hv/hyperv_vmbus.h          |   3 -
>  drivers/hv/vmbus_drv.c             |  42 ++++----
>  include/clocksource/hyperv_timer.h |  27 ++++++
>  10 files changed, 258 insertions(+), 175 deletions(-)
>  create mode 100644 drivers/clocksource/hyperv_timer.c
>  create mode 100644 include/clocksource/hyperv_timer.h
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 992f1dd..cf2a5b7 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -7294,6 +7294,7 @@ F:	arch/x86/include/asm/trace/hyperv.h
>  F:	arch/x86/include/asm/hyperv-tlfs.h
>  F:	arch/x86/kernel/cpu/mshyperv.c
>  F:	arch/x86/hyperv
> +F:	drivers/clocksource/hyperv_timer.c
>  F:	drivers/hid/hid-hyperv.c
>  F:	drivers/hv/
>  F:	drivers/input/serio/hyperv-keyboard.c
> @@ -7304,6 +7305,7 @@ F:	drivers/uio/uio_hv_generic.c
>  F:	drivers/video/fbdev/hyperv_fb.c
>  F:	drivers/iommu/hyperv_iommu.c
>  F:	net/vmw_vsock/hyperv_transport.c
> +F:	include/clocksource/hyperv_timer.h
>  F:	include/linux/hyperv.h
>  F:	include/uapi/linux/hyperv.h
>  F:	tools/hv/
> diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
> index cdf44aa..af78cd7 100644
> --- a/arch/x86/include/asm/hyperv-tlfs.h
> +++ b/arch/x86/include/asm/hyperv-tlfs.h
> @@ -401,6 +401,12 @@ enum HV_GENERIC_SET_FORMAT {
>  #define HV_STATUS_INVALID_CONNECTION_ID		18
>  #define HV_STATUS_INSUFFICIENT_BUFFERS		19
>  
> +/*
> + * The Hyper-V TimeRefCount register and the TSC
> + * page provide a guest VM clock with 100ns tick rate
> + */
> +#define HV_CLOCK_HZ (NSEC_PER_SEC/100)
> +
>  typedef struct _HV_REFERENCE_TSC_PAGE {
>  	__u32 tsc_sequence;
>  	__u32 res1;
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index faae611..b18ede4 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -21,6 +21,7 @@
>  #include <linux/irq.h>
>  #include <linux/kexec.h>
>  #include <linux/i8253.h>
> +#include <linux/random.h>
>  #include <asm/processor.h>
>  #include <asm/hypervisor.h>
>  #include <asm/hyperv-tlfs.h>
> @@ -84,6 +85,7 @@ __visible void __irq_entry hv_stimer0_vector_handler(struct pt_regs *regs)
>  	inc_irq_stat(hyperv_stimer0_count);
>  	if (hv_stimer0_handler)
>  		hv_stimer0_handler();
> +	add_interrupt_randomness(HYPERV_STIMER0_VECTOR, 0);
>  	ack_APIC_irq();
>  
>  	exiting_irq();
> diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
> index 236858f..2b65c5f 100644
> --- a/drivers/clocksource/Makefile
> +++ b/drivers/clocksource/Makefile
> @@ -84,3 +84,4 @@ obj-$(CONFIG_ATCPIT100_TIMER)		+= timer-atcpit100.o
>  obj-$(CONFIG_RISCV_TIMER)		+= timer-riscv.o
>  obj-$(CONFIG_CSKY_MP_TIMER)		+= timer-mp-csky.o
>  obj-$(CONFIG_GX6605S_TIMER)		+= timer-gx6605s.o
> +obj-$(CONFIG_HYPERV_TIMER)		+= hyperv_timer.o
> diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
> new file mode 100644
> index 0000000..30615f3
> --- /dev/null
> +++ b/drivers/clocksource/hyperv_timer.c
> @@ -0,0 +1,191 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +/*
> + * Clocksource driver for the synthetic counter and timers
> + * provided by the Hyper-V hypervisor to guest VMs, as described
> + * in the Hyper-V Top Level Functional Spec (TLFS). This driver
> + * is instruction set architecture independent.
> + *
> + * Copyright (C) 2019, Microsoft, Inc.
> + *
> + * Author:  Michael Kelley <mikelley@microsoft.com>
> + */
> +
> +#include <linux/percpu.h>
> +#include <linux/cpumask.h>
> +#include <linux/clockchips.h>
> +#include <linux/mm.h>
> +#include <clocksource/hyperv_timer.h>
> +#include <asm/hyperv-tlfs.h>
> +#include <asm/mshyperv.h>
> +
> +static struct clock_event_device __percpu *hv_clock_event;
> +
> +/*
> + * If false, we're using the old mechanism for stimer0 interrupts
> + * where it sends a VMbus message when it expires. The old
> + * mechanism is used when running on older versions of Hyper-V
> + * that don't support Direct Mode. While Hyper-V provides
> + * four stimer's per CPU, Linux uses only stimer0.
> + */
> +static bool direct_mode_enabled;
> +
> +static int stimer0_irq;
> +static int stimer0_vector;
> +static int stimer0_message_sint;
> +
> +/*
> + * ISR for when stimer0 is operating in Direct Mode.  Direct Mode
> + * does not use VMbus or any VMbus messages, so process here and not
> + * in the VMbus driver code.
> + */
> +void hv_stimer0_isr(void)
> +{
> +	struct clock_event_device *ce;
> +
> +	ce = this_cpu_ptr(hv_clock_event);
> +	ce->event_handler(ce);
> +}
> +EXPORT_SYMBOL_GPL(hv_stimer0_isr);
> +
> +static int hv_ce_set_next_event(unsigned long delta,
> +				struct clock_event_device *evt)
> +{
> +	u64 current_tick;
> +
> +	WARN_ON(!clockevent_state_oneshot(evt));
> +
> +	current_tick = hyperv_cs->read(NULL);
> +	current_tick += delta;
> +	hv_init_timer(0, current_tick);
> +	return 0;
> +}
> +
> +static int hv_ce_shutdown(struct clock_event_device *evt)
> +{
> +	hv_init_timer(0, 0);
> +	hv_init_timer_config(0, 0);
> +	if (direct_mode_enabled)
> +		hv_disable_stimer0_percpu_irq(stimer0_irq);
> +
> +	return 0;
> +}
> +
> +static int hv_ce_set_oneshot(struct clock_event_device *evt)
> +{
> +	union hv_stimer_config timer_cfg;
> +
> +	timer_cfg.as_uint64 = 0;
> +	timer_cfg.enable = 1;
> +	timer_cfg.auto_enable = 1;
> +	if (direct_mode_enabled) {
> +		/*
> +		 * When it expires, the timer will directly interrupt
> +		 * on the specified hardware vector/IRQ.
> +		 */
> +		timer_cfg.direct_mode = 1;
> +		timer_cfg.apic_vector = stimer0_vector;
> +		hv_enable_stimer0_percpu_irq(stimer0_irq);
> +	} else {
> +		/*
> +		 * When it expires, the timer will generate a VMbus message,
> +		 * to be handled by the normal VMbus interrupt handler.
> +		 */
> +		timer_cfg.direct_mode = 0;
> +		timer_cfg.sintx = stimer0_message_sint;
> +	}
> +	hv_init_timer_config(0, timer_cfg.as_uint64);
> +	return 0;
> +}
> +
> +/*
> + * hv_stimer_init - Per-cpu initialization of the clockevent
> + */
> +int hv_stimer_init(unsigned int cpu)
> +{
> +	struct clock_event_device *ce;
> +
> +	if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE) {
> +		ce = per_cpu_ptr(hv_clock_event, cpu);
> +		ce->name = "Hyper-V clockevent";
> +		ce->features = CLOCK_EVT_FEAT_ONESHOT;
> +		ce->cpumask = cpumask_of(cpu);
> +		ce->rating = 1000;
> +		ce->set_state_shutdown = hv_ce_shutdown;
> +		ce->set_state_oneshot = hv_ce_set_oneshot;
> +		ce->set_next_event = hv_ce_set_next_event;
> +
> +		clockevents_config_and_register(ce,
> +						HV_CLOCK_HZ,
> +						HV_MIN_DELTA_TICKS,
> +						HV_MAX_MAX_DELTA_TICKS);
> +	}
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(hv_stimer_init);
> +
> +/*
> + * hv_stimer_cleanup - Per-cpu cleanup of the clockevent
> + */
> +int hv_stimer_cleanup(unsigned int cpu)
> +{
> +	struct clock_event_device *ce;
> +
> +	/* Turn off clockevent device */
> +	if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE) {
> +		ce = per_cpu_ptr(hv_clock_event, cpu);
> +		clockevents_unbind_device(ce, cpu);
> +		hv_ce_shutdown(ce);
> +	}
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(hv_stimer_cleanup);
> +
> +/* hv_stimer_alloc - Global initialization of the clockevent and stimer0 */
> +int hv_stimer_alloc(int sint)
> +{
> +	hv_clock_event = alloc_percpu(struct clock_event_device);
> +	if (!hv_clock_event)
> +		return -ENOMEM;
> +
> +	direct_mode_enabled = ms_hyperv.misc_features &
> +			HV_STIMER_DIRECT_MODE_AVAILABLE;
> +	if (direct_mode_enabled &&
> +	    hv_setup_stimer0_irq(&stimer0_irq, &stimer0_vector,
> +				hv_stimer0_isr)) {
> +		free_percpu(hv_clock_event);
> +		return -EINVAL;
> +	}
> +
> +	stimer0_message_sint = sint;
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(hv_stimer_alloc);
> +
> +/* hv_stimer_free - Free global resources allocated by hv_stimer_alloc() */
> +void hv_stimer_free(void)
> +{
> +	if (direct_mode_enabled)
> +		hv_remove_stimer0_irq(stimer0_irq);
> +	free_percpu(hv_clock_event);
> +}
> +EXPORT_SYMBOL_GPL(hv_stimer_free);
> +
> +/*
> + * Do a global cleanup of clockevents for the cases of kexec and
> + * vmbus exit
> + */
> +void hv_stimer_global_cleanup(void)
> +{
> +	int	cpu;
> +	struct clock_event_device *ce;
> +
> +	if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE)
> +		for_each_present_cpu(cpu) {
> +			ce = per_cpu_ptr(hv_clock_event, cpu);
> +			clockevents_unbind_device(ce, cpu);
> +		}
> +	hv_stimer_free();
> +}
> +EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup);
> diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
> index 1c1a251..c423e57 100644
> --- a/drivers/hv/Kconfig
> +++ b/drivers/hv/Kconfig
> @@ -10,6 +10,9 @@ config HYPERV
>  	  Select this option to run Linux as a Hyper-V client operating
>  	  system.
>  
> +config HYPERV_TIMER
> +	def_bool HYPERV
> +
>  config HYPERV_TSCPAGE
>         def_bool HYPERV && X86_64
>  
> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index 4565302..bd6452f 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -29,6 +29,7 @@
>  #include <linux/version.h>
>  #include <linux/random.h>
>  #include <linux/clockchips.h>

(very minor nit, just an idea for future cleanup):

I think we can throw away

 #include <linux/random.h>
 #include <linux/clockchips.h>

now.

> +#include <clocksource/hyperv_timer.h>
>  #include <asm/mshyperv.h>
>  #include "hyperv_vmbus.h"
>  
> @@ -36,21 +37,6 @@
>  struct hv_context hv_context;
>  
>  /*
> - * If false, we're using the old mechanism for stimer0 interrupts
> - * where it sends a VMbus message when it expires. The old
> - * mechanism is used when running on older versions of Hyper-V
> - * that don't support Direct Mode. While Hyper-V provides
> - * four stimer's per CPU, Linux uses only stimer0.
> - */
> -static bool direct_mode_enabled;
> -static int stimer0_irq;
> -static int stimer0_vector;
> -
> -#define HV_TIMER_FREQUENCY (10 * 1000 * 1000) /* 100ns period */
> -#define HV_MAX_MAX_DELTA_TICKS 0xffffffff
> -#define HV_MIN_DELTA_TICKS 1
> -
> -/*
>   * hv_init - Main initialization routine.
>   *
>   * This routine must be called before any other routines in here are called
> @@ -60,9 +46,6 @@ int hv_init(void)
>  	hv_context.cpu_context = alloc_percpu(struct hv_per_cpu_context);
>  	if (!hv_context.cpu_context)
>  		return -ENOMEM;
> -
> -	direct_mode_enabled = ms_hyperv.misc_features &
> -			HV_STIMER_DIRECT_MODE_AVAILABLE;
>  	return 0;
>  }
>  
> @@ -101,89 +84,6 @@ int hv_post_message(union hv_connection_id connection_id,
>  	return status & 0xFFFF;
>  }
>  
> -/*
> - * ISR for when stimer0 is operating in Direct Mode.  Direct Mode
> - * does not use VMbus or any VMbus messages, so process here and not
> - * in the VMbus driver code.
> - */
> -
> -static void hv_stimer0_isr(void)
> -{
> -	struct hv_per_cpu_context *hv_cpu;
> -
> -	hv_cpu = this_cpu_ptr(hv_context.cpu_context);
> -	hv_cpu->clk_evt->event_handler(hv_cpu->clk_evt);
> -	add_interrupt_randomness(stimer0_vector, 0);
> -}
> -
> -static int hv_ce_set_next_event(unsigned long delta,
> -				struct clock_event_device *evt)
> -{
> -	u64 current_tick;
> -
> -	WARN_ON(!clockevent_state_oneshot(evt));
> -
> -	current_tick = hyperv_cs->read(NULL);
> -	current_tick += delta;
> -	hv_init_timer(0, current_tick);
> -	return 0;
> -}
> -
> -static int hv_ce_shutdown(struct clock_event_device *evt)
> -{
> -	hv_init_timer(0, 0);
> -	hv_init_timer_config(0, 0);
> -	if (direct_mode_enabled)
> -		hv_disable_stimer0_percpu_irq(stimer0_irq);
> -
> -	return 0;
> -}
> -
> -static int hv_ce_set_oneshot(struct clock_event_device *evt)
> -{
> -	union hv_stimer_config timer_cfg;
> -
> -	timer_cfg.as_uint64 = 0;
> -	timer_cfg.enable = 1;
> -	timer_cfg.auto_enable = 1;
> -	if (direct_mode_enabled) {
> -		/*
> -		 * When it expires, the timer will directly interrupt
> -		 * on the specified hardware vector/IRQ.
> -		 */
> -		timer_cfg.direct_mode = 1;
> -		timer_cfg.apic_vector = stimer0_vector;
> -		hv_enable_stimer0_percpu_irq(stimer0_irq);
> -	} else {
> -		/*
> -		 * When it expires, the timer will generate a VMbus message,
> -		 * to be handled by the normal VMbus interrupt handler.
> -		 */
> -		timer_cfg.direct_mode = 0;
> -		timer_cfg.sintx = VMBUS_MESSAGE_SINT;
> -	}
> -	hv_init_timer_config(0, timer_cfg.as_uint64);
> -	return 0;
> -}
> -
> -static void hv_init_clockevent_device(struct clock_event_device *dev, int cpu)
> -{
> -	dev->name = "Hyper-V clockevent";
> -	dev->features = CLOCK_EVT_FEAT_ONESHOT;
> -	dev->cpumask = cpumask_of(cpu);
> -	dev->rating = 1000;
> -	/*
> -	 * Avoid settint dev->owner = THIS_MODULE deliberately as doing so will
> -	 * result in clockevents_config_and_register() taking additional
> -	 * references to the hv_vmbus module making it impossible to unload.
> -	 */
> -
> -	dev->set_state_shutdown = hv_ce_shutdown;
> -	dev->set_state_oneshot = hv_ce_set_oneshot;
> -	dev->set_next_event = hv_ce_set_next_event;
> -}
> -
> -
>  int hv_synic_alloc(void)
>  {
>  	int cpu;
> @@ -212,14 +112,6 @@ int hv_synic_alloc(void)
>  		tasklet_init(&hv_cpu->msg_dpc,
>  			     vmbus_on_msg_dpc, (unsigned long) hv_cpu);
>  
> -		hv_cpu->clk_evt = kzalloc(sizeof(struct clock_event_device),
> -					  GFP_KERNEL);
> -		if (hv_cpu->clk_evt == NULL) {
> -			pr_err("Unable to allocate clock event device\n");
> -			goto err;
> -		}
> -		hv_init_clockevent_device(hv_cpu->clk_evt, cpu);
> -
>  		hv_cpu->synic_message_page =
>  			(void *)get_zeroed_page(GFP_ATOMIC);
>  		if (hv_cpu->synic_message_page == NULL) {
> @@ -242,11 +134,6 @@ int hv_synic_alloc(void)
>  		INIT_LIST_HEAD(&hv_cpu->chan_list);
>  	}
>  
> -	if (direct_mode_enabled &&
> -	    hv_setup_stimer0_irq(&stimer0_irq, &stimer0_vector,
> -				hv_stimer0_isr))
> -		goto err;
> -
>  	return 0;
>  err:
>  	/*
> @@ -265,7 +152,6 @@ void hv_synic_free(void)
>  		struct hv_per_cpu_context *hv_cpu
>  			= per_cpu_ptr(hv_context.cpu_context, cpu);
>  
> -		kfree(hv_cpu->clk_evt);
>  		free_page((unsigned long)hv_cpu->synic_event_page);
>  		free_page((unsigned long)hv_cpu->synic_message_page);
>  		free_page((unsigned long)hv_cpu->post_msg_page);
> @@ -324,36 +210,9 @@ int hv_synic_init(unsigned int cpu)
>  
>  	hv_set_synic_state(sctrl.as_uint64);
>  
> -	/*
> -	 * Register the per-cpu clockevent source.
> -	 */
> -	if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE)
> -		clockevents_config_and_register(hv_cpu->clk_evt,
> -						HV_TIMER_FREQUENCY,
> -						HV_MIN_DELTA_TICKS,
> -						HV_MAX_MAX_DELTA_TICKS);
> -	return 0;
> -}
> -
> -/*
> - * hv_synic_clockevents_cleanup - Cleanup clockevent devices
> - */
> -void hv_synic_clockevents_cleanup(void)
> -{
> -	int cpu;
> +	hv_stimer_init(cpu);
>  
> -	if (!(ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE))
> -		return;
> -
> -	if (direct_mode_enabled)
> -		hv_remove_stimer0_irq(stimer0_irq);
> -
> -	for_each_present_cpu(cpu) {
> -		struct hv_per_cpu_context *hv_cpu
> -			= per_cpu_ptr(hv_context.cpu_context, cpu);
> -
> -		clockevents_unbind_device(hv_cpu->clk_evt, cpu);
> -	}
> +	return 0;
>  }
>  
>  /*
> @@ -401,14 +260,7 @@ int hv_synic_cleanup(unsigned int cpu)
>  	if (channel_found && vmbus_connection.conn_state == CONNECTED)
>  		return -EBUSY;
>  
> -	/* Turn off clockevent device */
> -	if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE) {
> -		struct hv_per_cpu_context *hv_cpu
> -			= this_cpu_ptr(hv_context.cpu_context);
> -
> -		clockevents_unbind_device(hv_cpu->clk_evt, cpu);
> -		hv_ce_shutdown(hv_cpu->clk_evt);
> -	}
> +	hv_stimer_cleanup(cpu);
>  
>  	hv_get_synint_state(VMBUS_MESSAGE_SINT, shared_sint.as_uint64);
>  
> diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
> index e5467b8..a8f8aee 100644
> --- a/drivers/hv/hyperv_vmbus.h
> +++ b/drivers/hv/hyperv_vmbus.h
> @@ -151,7 +151,6 @@ struct hv_per_cpu_context {
>  	 * per-cpu list of the channels based on their CPU affinity.
>  	 */
>  	struct list_head chan_list;
> -	struct clock_event_device *clk_evt;
>  };
>  
>  struct hv_context {
> @@ -189,8 +188,6 @@ extern int hv_post_message(union hv_connection_id connection_id,
>  
>  extern int hv_synic_cleanup(unsigned int cpu);
>  
> -extern void hv_synic_clockevents_cleanup(void);
> -
>  /* Interface */
>  
>  void hv_ringbuffer_pre_init(struct vmbus_channel *channel);
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index 1cb9408..89aca5d 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -43,6 +43,7 @@
>  #include <linux/kdebug.h>
>  #include <linux/efi.h>
>  #include <linux/random.h>
> +#include <clocksource/hyperv_timer.h>
>  #include "hyperv_vmbus.h"
>  
>  struct vmbus_dynid {
> @@ -968,17 +969,6 @@ static void vmbus_onmessage_work(struct work_struct *work)
>  	kfree(ctx);
>  }
>  
> -static void hv_process_timer_expiration(struct hv_message *msg,
> -					struct hv_per_cpu_context *hv_cpu)
> -{
> -	struct clock_event_device *dev = hv_cpu->clk_evt;
> -
> -	if (dev->event_handler)
> -		dev->event_handler(dev);
> -
> -	vmbus_signal_eom(msg, HVMSG_TIMER_EXPIRED);
> -}
> -
>  void vmbus_on_msg_dpc(unsigned long data)
>  {
>  	struct hv_per_cpu_context *hv_cpu = (void *)data;
> @@ -1172,9 +1162,10 @@ static void vmbus_isr(void)
>  
>  	/* Check if there are actual msgs to be processed */
>  	if (msg->header.message_type != HVMSG_NONE) {
> -		if (msg->header.message_type == HVMSG_TIMER_EXPIRED)
> -			hv_process_timer_expiration(msg, hv_cpu);
> -		else
> +		if (msg->header.message_type == HVMSG_TIMER_EXPIRED) {
> +			hv_stimer0_isr();
> +			vmbus_signal_eom(msg, HVMSG_TIMER_EXPIRED);
> +		} else
>  			tasklet_schedule(&hv_cpu->msg_dpc);
>  	}
>  
> @@ -1276,14 +1267,19 @@ static int vmbus_bus_init(void)
>  	ret = hv_synic_alloc();
>  	if (ret)
>  		goto err_alloc;
> +
> +	ret = hv_stimer_alloc(VMBUS_MESSAGE_SINT);
> +	if (ret < 0)
> +		goto err_alloc;
> +
>  	/*
> -	 * Initialize the per-cpu interrupt state and
> -	 * connect to the host.
> +	 * Initialize the per-cpu interrupt state and stimer state.
> +	 * Then connect to the host.
>  	 */
>  	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "hyperv/vmbus:online",
>  				hv_synic_init, hv_synic_cleanup);
>  	if (ret < 0)
> -		goto err_alloc;
> +		goto err_cpuhp;
>  	hyperv_cpuhp_online = ret;
>  
>  	ret = vmbus_connect();
> @@ -1331,6 +1327,8 @@ static int vmbus_bus_init(void)
>  
>  err_connect:
>  	cpuhp_remove_state(hyperv_cpuhp_online);
> +err_cpuhp:
> +	hv_stimer_free();
>  err_alloc:
>  	hv_synic_free();
>  	hv_remove_vmbus_irq();
> @@ -2077,7 +2075,7 @@ static int vmbus_acpi_add(struct acpi_device *device)
>  
>  static void hv_kexec_handler(void)
>  {
> -	hv_synic_clockevents_cleanup();
> +	hv_stimer_global_cleanup();
>  	vmbus_initiate_unload(false);
>  	vmbus_connection.conn_state = DISCONNECTED;
>  	/* Make sure conn_state is set as hv_synic_cleanup checks for it */
> @@ -2088,6 +2086,8 @@ static void hv_kexec_handler(void)
>  
>  static void hv_crash_handler(struct pt_regs *regs)
>  {
> +	int cpu;
> +
>  	vmbus_initiate_unload(true);
>  	/*
>  	 * In crash handler we can't schedule synic cleanup for all CPUs,
> @@ -2095,7 +2095,9 @@ static void hv_crash_handler(struct pt_regs *regs)
>  	 * for kdump.
>  	 */
>  	vmbus_connection.conn_state = DISCONNECTED;
> -	hv_synic_cleanup(smp_processor_id());
> +	cpu = smp_processor_id();
> +	hv_stimer_cleanup(cpu);
> +	hv_synic_cleanup(cpu);
>  	hyperv_cleanup();
>  };
>  
> @@ -2144,7 +2146,7 @@ static void __exit vmbus_exit(void)
>  	hv_remove_kexec_handler();
>  	hv_remove_crash_handler();
>  	vmbus_connection.conn_state = DISCONNECTED;
> -	hv_synic_clockevents_cleanup();
> +	hv_stimer_global_cleanup();
>  	vmbus_disconnect();
>  	hv_remove_vmbus_irq();
>  	for_each_online_cpu(cpu) {
> diff --git a/include/clocksource/hyperv_timer.h b/include/clocksource/hyperv_timer.h
> new file mode 100644
> index 0000000..ba5dc17
> --- /dev/null
> +++ b/include/clocksource/hyperv_timer.h
> @@ -0,0 +1,27 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +/*
> + * Definitions for the clocksource provided by the Hyper-V
> + * hypervisor to guest VMs, as described in the Hyper-V Top
> + * Level Functional Spec (TLFS).
> + *
> + * Copyright (C) 2019, Microsoft, Inc.
> + *
> + * Author:  Michael Kelley <mikelley@microsoft.com>
> + */
> +
> +#ifndef __CLKSOURCE_HYPERV_TIMER_H
> +#define __CLKSOURCE_HYPERV_TIMER_H
> +
> +#define HV_MAX_MAX_DELTA_TICKS 0xffffffff
> +#define HV_MIN_DELTA_TICKS 1
> +
> +/* Routines called by the VMbus driver */
> +extern int hv_stimer_alloc(int sint);
> +extern void hv_stimer_free(void);
> +extern int hv_stimer_init(unsigned int cpu);
> +extern int hv_stimer_cleanup(unsigned int cpu);
> +extern void hv_stimer_global_cleanup(void);
> +extern void hv_stimer0_isr(void);
> +
> +#endif

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>

-- 
Vitaly

[PATCH v3 2/2] Drivers: hv: Move Hyper-V clocksource code to new clocksource driver

[Michael Kelley]

Code for the Hyper-V specific clocksources is currently mixed
in with other Hyper-V code. Move the code to the Hyper-V specific
driver in the "clocksource" directory, while separating out
ISA dependencies so that the clocksource driver remains ISA
independent. Update the Hyper-V initialization code to call
initialization and cleanup routines since the Hyper-V synthetic
timers are not independently enumerated in ACPI. Update Hyper-V
clocksource users KVM and VDSO to get definitions from a new
include file.

No behavior is changed and no new functionality is added.

Suggested-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Michael Kelley <mikelley@microsoft.com>
---
 arch/x86/entry/vdso/vclock_gettime.c |   1 +
 arch/x86/entry/vdso/vma.c            |   2 +-
 arch/x86/hyperv/hv_init.c            |  91 +-----------------------
 arch/x86/include/asm/mshyperv.h      |  81 +++-------------------
 arch/x86/kvm/x86.c                   |   1 +
 drivers/clocksource/hyperv_timer.c   | 130 +++++++++++++++++++++++++++++++++++
 drivers/hv/hv_util.c                 |   1 +
 include/clocksource/hyperv_timer.h   |  78 +++++++++++++++++++++
 8 files changed, 226 insertions(+), 159 deletions(-)

diff --git a/arch/x86/entry/vdso/vclock_gettime.c b/arch/x86/entry/vdso/vclock_gettime.c
index 98c7d12..7983ca2 100644
--- a/arch/x86/entry/vdso/vclock_gettime.c
+++ b/arch/x86/entry/vdso/vclock_gettime.c
@@ -21,6 +21,7 @@
 #include <linux/math64.h>
 #include <linux/time.h>
 #include <linux/kernel.h>
+#include <clocksource/hyperv_timer.h>
 
 #define gtod (&VVAR(vsyscall_gtod_data))
 
diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index babc4e7..99b38e9 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -22,7 +22,7 @@
 #include <asm/page.h>
 #include <asm/desc.h>
 #include <asm/cpufeature.h>
-#include <asm/mshyperv.h>
+#include <clocksource/hyperv_timer.h>
 
 #if defined(CONFIG_X86_64)
 unsigned int __read_mostly vdso64_enabled = 1;
diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index e4ba467..79f626a 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -27,64 +27,13 @@
 #include <linux/version.h>
 #include <linux/vmalloc.h>
 #include <linux/mm.h>
-#include <linux/clockchips.h>
 #include <linux/hyperv.h>
 #include <linux/slab.h>
 #include <linux/cpuhotplug.h>
-
-#ifdef CONFIG_HYPERV_TSCPAGE
-
-static struct ms_hyperv_tsc_page *tsc_pg;
-
-struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
-{
-	return tsc_pg;
-}
-EXPORT_SYMBOL_GPL(hv_get_tsc_page);
-
-static u64 read_hv_clock_tsc(struct clocksource *arg)
-{
-	u64 current_tick = hv_read_tsc_page(tsc_pg);
-
-	if (current_tick == U64_MAX)
-		rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);
-
-	return current_tick;
-}
-
-static struct clocksource hyperv_cs_tsc = {
-		.name		= "hyperv_clocksource_tsc_page",
-		.rating		= 400,
-		.read		= read_hv_clock_tsc,
-		.mask		= CLOCKSOURCE_MASK(64),
-		.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
-};
-#endif
-
-static u64 read_hv_clock_msr(struct clocksource *arg)
-{
-	u64 current_tick;
-	/*
-	 * Read the partition counter to get the current tick count. This count
-	 * is set to 0 when the partition is created and is incremented in
-	 * 100 nanosecond units.
-	 */
-	rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);
-	return current_tick;
-}
-
-static struct clocksource hyperv_cs_msr = {
-	.name		= "hyperv_clocksource_msr",
-	.rating		= 400,
-	.read		= read_hv_clock_msr,
-	.mask		= CLOCKSOURCE_MASK(64),
-	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
-};
+#include <clocksource/hyperv_timer.h>
 
 void *hv_hypercall_pg;
 EXPORT_SYMBOL_GPL(hv_hypercall_pg);
-struct clocksource *hyperv_cs;
-EXPORT_SYMBOL_GPL(hyperv_cs);
 
 u32 *hv_vp_index;
 EXPORT_SYMBOL_GPL(hv_vp_index);
@@ -353,42 +302,8 @@ void __init hyperv_init(void)
 
 	x86_init.pci.arch_init = hv_pci_init;
 
-	/*
-	 * Register Hyper-V specific clocksource.
-	 */
-#ifdef CONFIG_HYPERV_TSCPAGE
-	if (ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE) {
-		union hv_x64_msr_hypercall_contents tsc_msr;
-
-		tsc_pg = __vmalloc(PAGE_SIZE, GFP_KERNEL, PAGE_KERNEL);
-		if (!tsc_pg)
-			goto register_msr_cs;
-
-		hyperv_cs = &hyperv_cs_tsc;
-
-		rdmsrl(HV_X64_MSR_REFERENCE_TSC, tsc_msr.as_uint64);
-
-		tsc_msr.enable = 1;
-		tsc_msr.guest_physical_address = vmalloc_to_pfn(tsc_pg);
-
-		wrmsrl(HV_X64_MSR_REFERENCE_TSC, tsc_msr.as_uint64);
-
-		hyperv_cs_tsc.archdata.vclock_mode = VCLOCK_HVCLOCK;
-
-		clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);
-		return;
-	}
-register_msr_cs:
-#endif
-	/*
-	 * For 32 bit guests just use the MSR based mechanism for reading
-	 * the partition counter.
-	 */
-
-	hyperv_cs = &hyperv_cs_msr;
-	if (ms_hyperv.features & HV_MSR_TIME_REF_COUNT_AVAILABLE)
-		clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);
-
+	/* Register Hyper-V specific clocksource */
+	hv_init_clocksource();
 	return;
 
 remove_cpuhp_state:
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index cc60e61..f4fa8a9 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -105,6 +105,17 @@ static inline void vmbus_signal_eom(struct hv_message *msg, u32 old_msg_type)
 #define hv_get_crash_ctl(val) \
 	rdmsrl(HV_X64_MSR_CRASH_CTL, val)
 
+#define hv_get_time_ref_count(val) \
+	rdmsrl(HV_X64_MSR_TIME_REF_COUNT, val)
+
+#define hv_get_reference_tsc(val) \
+	rdmsrl(HV_X64_MSR_REFERENCE_TSC, val)
+#define hv_set_reference_tsc(val) \
+	wrmsrl(HV_X64_MSR_REFERENCE_TSC, val)
+#define hv_set_clocksource_vdso(val) \
+	((val).archdata.vclock_mode = VCLOCK_HVCLOCK)
+#define hv_get_raw_timer() rdtsc_ordered()
+
 void hyperv_callback_vector(void);
 void hyperv_reenlightenment_vector(void);
 #ifdef CONFIG_TRACING
@@ -133,7 +144,6 @@ static inline void hv_disable_stimer0_percpu_irq(int irq) {}
 
 
 #if IS_ENABLED(CONFIG_HYPERV)
-extern struct clocksource *hyperv_cs;
 extern void *hv_hypercall_pg;
 extern void  __percpu  **hyperv_pcpu_input_arg;
 
@@ -387,73 +397,4 @@ static inline int hyperv_flush_guest_mapping_range(u64 as,
 }
 #endif /* CONFIG_HYPERV */
 
-#ifdef CONFIG_HYPERV_TSCPAGE
-struct ms_hyperv_tsc_page *hv_get_tsc_page(void);
-static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg,
-				       u64 *cur_tsc)
-{
-	u64 scale, offset;
-	u32 sequence;
-
-	/*
-	 * The protocol for reading Hyper-V TSC page is specified in Hypervisor
-	 * Top-Level Functional Specification ver. 3.0 and above. To get the
-	 * reference time we must do the following:
-	 * - READ ReferenceTscSequence
-	 *   A special '0' value indicates the time source is unreliable and we
-	 *   need to use something else. The currently published specification
-	 *   versions (up to 4.0b) contain a mistake and wrongly claim '-1'
-	 *   instead of '0' as the special value, see commit c35b82ef0294.
-	 * - ReferenceTime =
-	 *        ((RDTSC() * ReferenceTscScale) >> 64) + ReferenceTscOffset
-	 * - READ ReferenceTscSequence again. In case its value has changed
-	 *   since our first reading we need to discard ReferenceTime and repeat
-	 *   the whole sequence as the hypervisor was updating the page in
-	 *   between.
-	 */
-	do {
-		sequence = READ_ONCE(tsc_pg->tsc_sequence);
-		if (!sequence)
-			return U64_MAX;
-		/*
-		 * Make sure we read sequence before we read other values from
-		 * TSC page.
-		 */
-		smp_rmb();
-
-		scale = READ_ONCE(tsc_pg->tsc_scale);
-		offset = READ_ONCE(tsc_pg->tsc_offset);
-		*cur_tsc = rdtsc_ordered();
-
-		/*
-		 * Make sure we read sequence after we read all other values
-		 * from TSC page.
-		 */
-		smp_rmb();
-
-	} while (READ_ONCE(tsc_pg->tsc_sequence) != sequence);
-
-	return mul_u64_u64_shr(*cur_tsc, scale, 64) + offset;
-}
-
-static inline u64 hv_read_tsc_page(const struct ms_hyperv_tsc_page *tsc_pg)
-{
-	u64 cur_tsc;
-
-	return hv_read_tsc_page_tsc(tsc_pg, &cur_tsc);
-}
-
-#else
-static inline struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
-{
-	return NULL;
-}
-
-static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg,
-				       u64 *cur_tsc)
-{
-	BUG();
-	return U64_MAX;
-}
-#endif
 #endif
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 536b78c..3fbaac0 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -70,6 +70,7 @@
 #include <asm/mshyperv.h>
 #include <asm/hypervisor.h>
 #include <asm/intel_pt.h>
+#include <clocksource/hyperv_timer.h>
 
 #define CREATE_TRACE_POINTS
 #include "trace.h"
diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
index 30615f3..274614d 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -14,6 +14,8 @@
 #include <linux/percpu.h>
 #include <linux/cpumask.h>
 #include <linux/clockchips.h>
+#include <linux/clocksource.h>
+#include <linux/sched_clock.h>
 #include <linux/mm.h>
 #include <clocksource/hyperv_timer.h>
 #include <asm/hyperv-tlfs.h>
@@ -189,3 +191,131 @@ void hv_stimer_global_cleanup(void)
 	hv_stimer_free();
 }
 EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup);
+
+/*
+ * Code and definitions for the Hyper-V clocksources.  Two
+ * clocksources are defined: one that reads the Hyper-V defined MSR, and
+ * 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.
+ */
+
+struct clocksource *hyperv_cs;
+EXPORT_SYMBOL_GPL(hyperv_cs);
+
+#ifdef CONFIG_HYPERV_TSCPAGE
+
+static struct ms_hyperv_tsc_page *tsc_pg;
+
+struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
+{
+	return tsc_pg;
+}
+EXPORT_SYMBOL_GPL(hv_get_tsc_page);
+
+static u64 read_hv_sched_clock_tsc(void)
+{
+	u64 current_tick = hv_read_tsc_page(tsc_pg);
+
+	if (current_tick == U64_MAX)
+		hv_get_time_ref_count(current_tick);
+
+	return current_tick;
+}
+
+static u64 read_hv_clock_tsc(struct clocksource *arg)
+{
+	return read_hv_sched_clock_tsc();
+}
+
+static struct clocksource hyperv_cs_tsc = {
+		.name		= "hyperv_clocksource_tsc_page",
+		.rating		= 400,
+		.read		= read_hv_clock_tsc,
+		.mask		= CLOCKSOURCE_MASK(64),
+		.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
+};
+#endif
+
+static u64 read_hv_sched_clock_msr(void)
+{
+	u64 current_tick;
+	/*
+	 * Read the partition counter to get the current tick count. This count
+	 * is set to 0 when the partition is created and is incremented in
+	 * 100 nanosecond units.
+	 */
+	hv_get_time_ref_count(current_tick);
+	return current_tick;
+}
+
+static u64 read_hv_clock_msr(struct clocksource *arg)
+{
+	return read_hv_sched_clock_msr();
+}
+
+static struct clocksource hyperv_cs_msr = {
+	.name		= "hyperv_clocksource_msr",
+	.rating		= 400,
+	.read		= read_hv_clock_msr,
+	.mask		= CLOCKSOURCE_MASK(64),
+	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+void __init hv_init_clocksource(void)
+{
+#ifdef CONFIG_HYPERV_TSCPAGE
+	if (ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE) {
+
+		u64		tsc_msr;
+		phys_addr_t	phys_addr;
+
+		tsc_pg = vmalloc(PAGE_SIZE);
+		if (!tsc_pg)
+			goto register_msr_cs;
+
+		hyperv_cs = &hyperv_cs_tsc;
+		phys_addr = page_to_phys(vmalloc_to_page(tsc_pg));
+
+		/* The Hyper-V TLFS specifies to preserve the value of
+		 * reserved bits in registers.  So read the existing
+		 * value, preserve the low order 12 bits, and add in
+		 * the guest physical address (which already has at
+		 * least the low 12 bits set to zero since it is page
+		 * aligned). Also set the "enable" bit, which is bit 0.
+		 */
+		hv_get_reference_tsc(tsc_msr);
+		tsc_msr &= GENMASK_ULL(11, 0);
+		tsc_msr = tsc_msr | 0x1 | (u64)phys_addr;
+		hv_set_reference_tsc(tsc_msr);
+
+		hv_set_clocksource_vdso(hyperv_cs_tsc);
+		clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);
+
+		/*
+		 * sched_clock_register is needed on ARM64 but
+		 * is a no-op on x86
+		 */
+		sched_clock_register(read_hv_sched_clock_tsc,
+						64, HV_CLOCK_HZ);
+		return;
+	}
+register_msr_cs:
+#endif
+	/*
+	 * For 32 bit guests just use the MSR based mechanism for reading
+	 * the partition counter.
+	 */
+	hyperv_cs = &hyperv_cs_msr;
+	if (ms_hyperv.features & HV_MSR_TIME_REF_COUNT_AVAILABLE) {
+		clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);
+
+		/*
+		 * sched_clock_register is needed on ARM64 but
+		 * is a no-op on x86
+		 */
+		sched_clock_register(read_hv_sched_clock_msr,
+						64, HV_CLOCK_HZ);
+	}
+}
+EXPORT_SYMBOL_GPL(hv_init_clocksource);
diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c
index f10eeb1..9eff85e 100644
--- a/drivers/hv/hv_util.c
+++ b/drivers/hv/hv_util.c
@@ -29,6 +29,7 @@
 #include <linux/hyperv.h>
 #include <linux/clockchips.h>
 #include <linux/ptp_clock_kernel.h>
+#include <clocksource/hyperv_timer.h>
 #include <asm/mshyperv.h>
 
 #include "hyperv_vmbus.h"
diff --git a/include/clocksource/hyperv_timer.h b/include/clocksource/hyperv_timer.h
index ba5dc17..e17e8a2 100644
--- a/include/clocksource/hyperv_timer.h
+++ b/include/clocksource/hyperv_timer.h
@@ -13,6 +13,10 @@
 #ifndef __CLKSOURCE_HYPERV_TIMER_H
 #define __CLKSOURCE_HYPERV_TIMER_H
 
+#include <linux/clocksource.h>
+#include <linux/math64.h>
+#include <asm/mshyperv.h>
+
 #define HV_MAX_MAX_DELTA_TICKS 0xffffffff
 #define HV_MIN_DELTA_TICKS 1
 
@@ -24,4 +28,78 @@
 extern void hv_stimer_global_cleanup(void);
 extern void hv_stimer0_isr(void);
 
+#if IS_ENABLED(CONFIG_HYPERV)
+extern struct clocksource *hyperv_cs;
+extern void hv_init_clocksource(void);
+#endif /* CONFIG_HYPERV */
+
+#ifdef CONFIG_HYPERV_TSCPAGE
+extern struct ms_hyperv_tsc_page *hv_get_tsc_page(void);
+static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg,
+				       u64 *cur_tsc)
+{
+	u64 scale, offset;
+	u32 sequence;
+
+	/*
+	 * The protocol for reading Hyper-V TSC page is specified in Hypervisor
+	 * Top-Level Functional Specification ver. 3.0 and above. To get the
+	 * reference time we must do the following:
+	 * - READ ReferenceTscSequence
+	 *   A special '0' value indicates the time source is unreliable and we
+	 *   need to use something else. The currently published specification
+	 *   versions (up to 4.0b) contain a mistake and wrongly claim '-1'
+	 *   instead of '0' as the special value, see commit c35b82ef0294.
+	 * - ReferenceTime =
+	 *        ((RDTSC() * ReferenceTscScale) >> 64) + ReferenceTscOffset
+	 * - READ ReferenceTscSequence again. In case its value has changed
+	 *   since our first reading we need to discard ReferenceTime and repeat
+	 *   the whole sequence as the hypervisor was updating the page in
+	 *   between.
+	 */
+	do {
+		sequence = READ_ONCE(tsc_pg->tsc_sequence);
+		if (!sequence)
+			return U64_MAX;
+		/*
+		 * Make sure we read sequence before we read other values from
+		 * TSC page.
+		 */
+		smp_rmb();
+
+		scale = READ_ONCE(tsc_pg->tsc_scale);
+		offset = READ_ONCE(tsc_pg->tsc_offset);
+		*cur_tsc = hv_get_raw_timer();
+
+		/*
+		 * Make sure we read sequence after we read all other values
+		 * from TSC page.
+		 */
+		smp_rmb();
+
+	} while (READ_ONCE(tsc_pg->tsc_sequence) != sequence);
+
+	return mul_u64_u64_shr(*cur_tsc, scale, 64) + offset;
+}
+
+static inline u64 hv_read_tsc_page(const struct ms_hyperv_tsc_page *tsc_pg)
+{
+	u64 cur_tsc;
+
+	return hv_read_tsc_page_tsc(tsc_pg, &cur_tsc);
+}
+
+#else /* CONFIG_HYPERV_TSC_PAGE */
+static inline struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
+{
+	return NULL;
+}
+
+static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg,
+				       u64 *cur_tsc)
+{
+	return U64_MAX;
+}
+#endif /* CONFIG_HYPERV_TSCPAGE */
+
 #endif
-- 
1.8.3.1

Re: [PATCH v3 2/2] Drivers: hv: Move Hyper-V clocksource code to new clocksource driver

[Vitaly Kuznetsov]

Michael Kelley <mikelley@microsoft.com> writes:

> Code for the Hyper-V specific clocksources is currently mixed
> in with other Hyper-V code. Move the code to the Hyper-V specific
> driver in the "clocksource" directory, while separating out
> ISA dependencies so that the clocksource driver remains ISA
> independent. Update the Hyper-V initialization code to call
> initialization and cleanup routines since the Hyper-V synthetic
> timers are not independently enumerated in ACPI. Update Hyper-V
> clocksource users KVM and VDSO to get definitions from a new
> include file.
>
> No behavior is changed and no new functionality is added.
>
> Suggested-by: Marc Zyngier <marc.zyngier@arm.com>
> Signed-off-by: Michael Kelley <mikelley@microsoft.com>
> ---
>  arch/x86/entry/vdso/vclock_gettime.c |   1 +
>  arch/x86/entry/vdso/vma.c            |   2 +-
>  arch/x86/hyperv/hv_init.c            |  91 +-----------------------
>  arch/x86/include/asm/mshyperv.h      |  81 +++-------------------
>  arch/x86/kvm/x86.c                   |   1 +
>  drivers/clocksource/hyperv_timer.c   | 130 +++++++++++++++++++++++++++++++++++
>  drivers/hv/hv_util.c                 |   1 +
>  include/clocksource/hyperv_timer.h   |  78 +++++++++++++++++++++
>  8 files changed, 226 insertions(+), 159 deletions(-)
>
> diff --git a/arch/x86/entry/vdso/vclock_gettime.c b/arch/x86/entry/vdso/vclock_gettime.c
> index 98c7d12..7983ca2 100644
> --- a/arch/x86/entry/vdso/vclock_gettime.c
> +++ b/arch/x86/entry/vdso/vclock_gettime.c
> @@ -21,6 +21,7 @@
>  #include <linux/math64.h>
>  #include <linux/time.h>
>  #include <linux/kernel.h>
> +#include <clocksource/hyperv_timer.h>
>  
>  #define gtod (&VVAR(vsyscall_gtod_data))
>  
> diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
> index babc4e7..99b38e9 100644
> --- a/arch/x86/entry/vdso/vma.c
> +++ b/arch/x86/entry/vdso/vma.c
> @@ -22,7 +22,7 @@
>  #include <asm/page.h>
>  #include <asm/desc.h>
>  #include <asm/cpufeature.h>
> -#include <asm/mshyperv.h>
> +#include <clocksource/hyperv_timer.h>
>  
>  #if defined(CONFIG_X86_64)
>  unsigned int __read_mostly vdso64_enabled = 1;
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index e4ba467..79f626a 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -27,64 +27,13 @@
>  #include <linux/version.h>
>  #include <linux/vmalloc.h>
>  #include <linux/mm.h>
> -#include <linux/clockchips.h>
>  #include <linux/hyperv.h>
>  #include <linux/slab.h>
>  #include <linux/cpuhotplug.h>
> -
> -#ifdef CONFIG_HYPERV_TSCPAGE
> -
> -static struct ms_hyperv_tsc_page *tsc_pg;
> -
> -struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
> -{
> -	return tsc_pg;
> -}
> -EXPORT_SYMBOL_GPL(hv_get_tsc_page);
> -
> -static u64 read_hv_clock_tsc(struct clocksource *arg)
> -{
> -	u64 current_tick = hv_read_tsc_page(tsc_pg);
> -
> -	if (current_tick == U64_MAX)
> -		rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);
> -
> -	return current_tick;
> -}
> -
> -static struct clocksource hyperv_cs_tsc = {
> -		.name		= "hyperv_clocksource_tsc_page",
> -		.rating		= 400,
> -		.read		= read_hv_clock_tsc,
> -		.mask		= CLOCKSOURCE_MASK(64),
> -		.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
> -};
> -#endif
> -
> -static u64 read_hv_clock_msr(struct clocksource *arg)
> -{
> -	u64 current_tick;
> -	/*
> -	 * Read the partition counter to get the current tick count. This count
> -	 * is set to 0 when the partition is created and is incremented in
> -	 * 100 nanosecond units.
> -	 */
> -	rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);
> -	return current_tick;
> -}
> -
> -static struct clocksource hyperv_cs_msr = {
> -	.name		= "hyperv_clocksource_msr",
> -	.rating		= 400,
> -	.read		= read_hv_clock_msr,
> -	.mask		= CLOCKSOURCE_MASK(64),
> -	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
> -};
> +#include <clocksource/hyperv_timer.h>
>  
>  void *hv_hypercall_pg;
>  EXPORT_SYMBOL_GPL(hv_hypercall_pg);
> -struct clocksource *hyperv_cs;
> -EXPORT_SYMBOL_GPL(hyperv_cs);
>  
>  u32 *hv_vp_index;
>  EXPORT_SYMBOL_GPL(hv_vp_index);
> @@ -353,42 +302,8 @@ void __init hyperv_init(void)
>  
>  	x86_init.pci.arch_init = hv_pci_init;
>  
> -	/*
> -	 * Register Hyper-V specific clocksource.
> -	 */
> -#ifdef CONFIG_HYPERV_TSCPAGE
> -	if (ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE) {
> -		union hv_x64_msr_hypercall_contents tsc_msr;
> -
> -		tsc_pg = __vmalloc(PAGE_SIZE, GFP_KERNEL, PAGE_KERNEL);
> -		if (!tsc_pg)
> -			goto register_msr_cs;
> -
> -		hyperv_cs = &hyperv_cs_tsc;
> -
> -		rdmsrl(HV_X64_MSR_REFERENCE_TSC, tsc_msr.as_uint64);
> -
> -		tsc_msr.enable = 1;
> -		tsc_msr.guest_physical_address = vmalloc_to_pfn(tsc_pg);
> -
> -		wrmsrl(HV_X64_MSR_REFERENCE_TSC, tsc_msr.as_uint64);
> -
> -		hyperv_cs_tsc.archdata.vclock_mode = VCLOCK_HVCLOCK;
> -
> -		clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);
> -		return;
> -	}
> -register_msr_cs:
> -#endif
> -	/*
> -	 * For 32 bit guests just use the MSR based mechanism for reading
> -	 * the partition counter.
> -	 */
> -
> -	hyperv_cs = &hyperv_cs_msr;
> -	if (ms_hyperv.features & HV_MSR_TIME_REF_COUNT_AVAILABLE)
> -		clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);
> -
> +	/* Register Hyper-V specific clocksource */
> +	hv_init_clocksource();
>  	return;
>  
>  remove_cpuhp_state:
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> index cc60e61..f4fa8a9 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -105,6 +105,17 @@ static inline void vmbus_signal_eom(struct hv_message *msg, u32 old_msg_type)
>  #define hv_get_crash_ctl(val) \
>  	rdmsrl(HV_X64_MSR_CRASH_CTL, val)
>  
> +#define hv_get_time_ref_count(val) \
> +	rdmsrl(HV_X64_MSR_TIME_REF_COUNT, val)
> +
> +#define hv_get_reference_tsc(val) \
> +	rdmsrl(HV_X64_MSR_REFERENCE_TSC, val)
> +#define hv_set_reference_tsc(val) \
> +	wrmsrl(HV_X64_MSR_REFERENCE_TSC, val)
> +#define hv_set_clocksource_vdso(val) \
> +	((val).archdata.vclock_mode = VCLOCK_HVCLOCK)
> +#define hv_get_raw_timer() rdtsc_ordered()
> +
>  void hyperv_callback_vector(void);
>  void hyperv_reenlightenment_vector(void);
>  #ifdef CONFIG_TRACING
> @@ -133,7 +144,6 @@ static inline void hv_disable_stimer0_percpu_irq(int irq) {}
>  
>  
>  #if IS_ENABLED(CONFIG_HYPERV)
> -extern struct clocksource *hyperv_cs;
>  extern void *hv_hypercall_pg;
>  extern void  __percpu  **hyperv_pcpu_input_arg;
>  
> @@ -387,73 +397,4 @@ static inline int hyperv_flush_guest_mapping_range(u64 as,
>  }
>  #endif /* CONFIG_HYPERV */
>  
> -#ifdef CONFIG_HYPERV_TSCPAGE
> -struct ms_hyperv_tsc_page *hv_get_tsc_page(void);
> -static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg,
> -				       u64 *cur_tsc)
> -{
> -	u64 scale, offset;
> -	u32 sequence;
> -
> -	/*
> -	 * The protocol for reading Hyper-V TSC page is specified in Hypervisor
> -	 * Top-Level Functional Specification ver. 3.0 and above. To get the
> -	 * reference time we must do the following:
> -	 * - READ ReferenceTscSequence
> -	 *   A special '0' value indicates the time source is unreliable and we
> -	 *   need to use something else. The currently published specification
> -	 *   versions (up to 4.0b) contain a mistake and wrongly claim '-1'
> -	 *   instead of '0' as the special value, see commit c35b82ef0294.
> -	 * - ReferenceTime =
> -	 *        ((RDTSC() * ReferenceTscScale) >> 64) + ReferenceTscOffset
> -	 * - READ ReferenceTscSequence again. In case its value has changed
> -	 *   since our first reading we need to discard ReferenceTime and repeat
> -	 *   the whole sequence as the hypervisor was updating the page in
> -	 *   between.
> -	 */
> -	do {
> -		sequence = READ_ONCE(tsc_pg->tsc_sequence);
> -		if (!sequence)
> -			return U64_MAX;
> -		/*
> -		 * Make sure we read sequence before we read other values from
> -		 * TSC page.
> -		 */
> -		smp_rmb();
> -
> -		scale = READ_ONCE(tsc_pg->tsc_scale);
> -		offset = READ_ONCE(tsc_pg->tsc_offset);
> -		*cur_tsc = rdtsc_ordered();
> -
> -		/*
> -		 * Make sure we read sequence after we read all other values
> -		 * from TSC page.
> -		 */
> -		smp_rmb();
> -
> -	} while (READ_ONCE(tsc_pg->tsc_sequence) != sequence);
> -
> -	return mul_u64_u64_shr(*cur_tsc, scale, 64) + offset;
> -}
> -
> -static inline u64 hv_read_tsc_page(const struct ms_hyperv_tsc_page *tsc_pg)
> -{
> -	u64 cur_tsc;
> -
> -	return hv_read_tsc_page_tsc(tsc_pg, &cur_tsc);
> -}
> -
> -#else
> -static inline struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
> -{
> -	return NULL;
> -}
> -
> -static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg,
> -				       u64 *cur_tsc)
> -{
> -	BUG();
> -	return U64_MAX;
> -}
> -#endif
>  #endif
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 536b78c..3fbaac0 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -70,6 +70,7 @@
>  #include <asm/mshyperv.h>
>  #include <asm/hypervisor.h>
>  #include <asm/intel_pt.h>
> +#include <clocksource/hyperv_timer.h>
>  
>  #define CREATE_TRACE_POINTS
>  #include "trace.h"
> diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
> index 30615f3..274614d 100644
> --- a/drivers/clocksource/hyperv_timer.c
> +++ b/drivers/clocksource/hyperv_timer.c
> @@ -14,6 +14,8 @@
>  #include <linux/percpu.h>
>  #include <linux/cpumask.h>
>  #include <linux/clockchips.h>
> +#include <linux/clocksource.h>
> +#include <linux/sched_clock.h>
>  #include <linux/mm.h>
>  #include <clocksource/hyperv_timer.h>
>  #include <asm/hyperv-tlfs.h>
> @@ -189,3 +191,131 @@ void hv_stimer_global_cleanup(void)
>  	hv_stimer_free();
>  }
>  EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup);
> +
> +/*
> + * Code and definitions for the Hyper-V clocksources.  Two
> + * clocksources are defined: one that reads the Hyper-V defined MSR, and
> + * 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.
> + */
> +
> +struct clocksource *hyperv_cs;
> +EXPORT_SYMBOL_GPL(hyperv_cs);
> +
> +#ifdef CONFIG_HYPERV_TSCPAGE
> +
> +static struct ms_hyperv_tsc_page *tsc_pg;
> +
> +struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
> +{
> +	return tsc_pg;
> +}
> +EXPORT_SYMBOL_GPL(hv_get_tsc_page);
> +
> +static u64 read_hv_sched_clock_tsc(void)
> +{
> +	u64 current_tick = hv_read_tsc_page(tsc_pg);
> +
> +	if (current_tick == U64_MAX)
> +		hv_get_time_ref_count(current_tick);
> +
> +	return current_tick;
> +}
> +
> +static u64 read_hv_clock_tsc(struct clocksource *arg)
> +{
> +	return read_hv_sched_clock_tsc();
> +}
> +
> +static struct clocksource hyperv_cs_tsc = {
> +		.name		= "hyperv_clocksource_tsc_page",
> +		.rating		= 400,
> +		.read		= read_hv_clock_tsc,
> +		.mask		= CLOCKSOURCE_MASK(64),
> +		.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
> +};
> +#endif
> +
> +static u64 read_hv_sched_clock_msr(void)
> +{
> +	u64 current_tick;
> +	/*
> +	 * Read the partition counter to get the current tick count. This count
> +	 * is set to 0 when the partition is created and is incremented in
> +	 * 100 nanosecond units.
> +	 */
> +	hv_get_time_ref_count(current_tick);
> +	return current_tick;
> +}
> +
> +static u64 read_hv_clock_msr(struct clocksource *arg)
> +{
> +	return read_hv_sched_clock_msr();
> +}
> +
> +static struct clocksource hyperv_cs_msr = {
> +	.name		= "hyperv_clocksource_msr",
> +	.rating		= 400,
> +	.read		= read_hv_clock_msr,
> +	.mask		= CLOCKSOURCE_MASK(64),
> +	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
> +};
> +
> +void __init hv_init_clocksource(void)
> +{
> +#ifdef CONFIG_HYPERV_TSCPAGE
> +	if (ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE) {
> +
> +		u64		tsc_msr;
> +		phys_addr_t	phys_addr;
> +
> +		tsc_pg = vmalloc(PAGE_SIZE);
> +		if (!tsc_pg)
> +			goto register_msr_cs;
> +
> +		hyperv_cs = &hyperv_cs_tsc;
> +		phys_addr = page_to_phys(vmalloc_to_page(tsc_pg));
> +
> +		/* The Hyper-V TLFS specifies to preserve the value of
> +		 * reserved bits in registers.  So read the existing
> +		 * value, preserve the low order 12 bits, and add in
> +		 * the guest physical address (which already has at
> +		 * least the low 12 bits set to zero since it is page
> +		 * aligned). Also set the "enable" bit, which is bit 0.
> +		 */
> +		hv_get_reference_tsc(tsc_msr);
> +		tsc_msr &= GENMASK_ULL(11, 0);
> +		tsc_msr = tsc_msr | 0x1 | (u64)phys_addr;
> +		hv_set_reference_tsc(tsc_msr);
> +
> +		hv_set_clocksource_vdso(hyperv_cs_tsc);
> +		clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);
> +
> +		/*
> +		 * sched_clock_register is needed on ARM64 but
> +		 * is a no-op on x86
> +		 */
> +		sched_clock_register(read_hv_sched_clock_tsc,
> +						64, HV_CLOCK_HZ);
> +		return;
> +	}
> +register_msr_cs:
> +#endif
> +	/*
> +	 * For 32 bit guests just use the MSR based mechanism for reading
> +	 * the partition counter.
> +	 */
> +	hyperv_cs = &hyperv_cs_msr;
> +	if (ms_hyperv.features & HV_MSR_TIME_REF_COUNT_AVAILABLE) {
> +		clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);
> +
> +		/*
> +		 * sched_clock_register is needed on ARM64 but
> +		 * is a no-op on x86
> +		 */
> +		sched_clock_register(read_hv_sched_clock_msr,
> +						64, HV_CLOCK_HZ);

I'm not sure about ARM, but MSR-based clocksource would be a really bad
choice for sched clock on x86, this will slow things down
significantly. Luckily, as you're validly stating above,
sched_clock_register() is a no-op on x86 as we don't define
CONFIG_GENERIC_SCHED_CLOCK.

Can we actually *not* do sched_clock_register() in case
TSC page is unavailable (and revert to counting jiffies or whatever)?

> +	}
> +}
> +EXPORT_SYMBOL_GPL(hv_init_clocksource);
> diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c
> index f10eeb1..9eff85e 100644
> --- a/drivers/hv/hv_util.c
> +++ b/drivers/hv/hv_util.c
> @@ -29,6 +29,7 @@
>  #include <linux/hyperv.h>
>  #include <linux/clockchips.h>
>  #include <linux/ptp_clock_kernel.h>
> +#include <clocksource/hyperv_timer.h>
>  #include <asm/mshyperv.h>
>  
>  #include "hyperv_vmbus.h"
> diff --git a/include/clocksource/hyperv_timer.h b/include/clocksource/hyperv_timer.h
> index ba5dc17..e17e8a2 100644
> --- a/include/clocksource/hyperv_timer.h
> +++ b/include/clocksource/hyperv_timer.h
> @@ -13,6 +13,10 @@
>  #ifndef __CLKSOURCE_HYPERV_TIMER_H
>  #define __CLKSOURCE_HYPERV_TIMER_H
>  
> +#include <linux/clocksource.h>
> +#include <linux/math64.h>
> +#include <asm/mshyperv.h>
> +
>  #define HV_MAX_MAX_DELTA_TICKS 0xffffffff
>  #define HV_MIN_DELTA_TICKS 1
>  
> @@ -24,4 +28,78 @@
>  extern void hv_stimer_global_cleanup(void);
>  extern void hv_stimer0_isr(void);
>  
> +#if IS_ENABLED(CONFIG_HYPERV)
> +extern struct clocksource *hyperv_cs;
> +extern void hv_init_clocksource(void);
> +#endif /* CONFIG_HYPERV */
> +
> +#ifdef CONFIG_HYPERV_TSCPAGE
> +extern struct ms_hyperv_tsc_page *hv_get_tsc_page(void);
> +static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg,
> +				       u64 *cur_tsc)
> +{
> +	u64 scale, offset;
> +	u32 sequence;
> +
> +	/*
> +	 * The protocol for reading Hyper-V TSC page is specified in Hypervisor
> +	 * Top-Level Functional Specification ver. 3.0 and above. To get the
> +	 * reference time we must do the following:
> +	 * - READ ReferenceTscSequence
> +	 *   A special '0' value indicates the time source is unreliable and we
> +	 *   need to use something else. The currently published specification
> +	 *   versions (up to 4.0b) contain a mistake and wrongly claim '-1'
> +	 *   instead of '0' as the special value, see commit c35b82ef0294.
> +	 * - ReferenceTime =
> +	 *        ((RDTSC() * ReferenceTscScale) >> 64) + ReferenceTscOffset
> +	 * - READ ReferenceTscSequence again. In case its value has changed
> +	 *   since our first reading we need to discard ReferenceTime and repeat
> +	 *   the whole sequence as the hypervisor was updating the page in
> +	 *   between.
> +	 */
> +	do {
> +		sequence = READ_ONCE(tsc_pg->tsc_sequence);
> +		if (!sequence)
> +			return U64_MAX;
> +		/*
> +		 * Make sure we read sequence before we read other values from
> +		 * TSC page.
> +		 */
> +		smp_rmb();
> +
> +		scale = READ_ONCE(tsc_pg->tsc_scale);
> +		offset = READ_ONCE(tsc_pg->tsc_offset);
> +		*cur_tsc = hv_get_raw_timer();
> +
> +		/*
> +		 * Make sure we read sequence after we read all other values
> +		 * from TSC page.
> +		 */
> +		smp_rmb();
> +
> +	} while (READ_ONCE(tsc_pg->tsc_sequence) != sequence);
> +
> +	return mul_u64_u64_shr(*cur_tsc, scale, 64) + offset;
> +}
> +
> +static inline u64 hv_read_tsc_page(const struct ms_hyperv_tsc_page *tsc_pg)
> +{
> +	u64 cur_tsc;
> +
> +	return hv_read_tsc_page_tsc(tsc_pg, &cur_tsc);
> +}
> +
> +#else /* CONFIG_HYPERV_TSC_PAGE */
> +static inline struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
> +{
> +	return NULL;
> +}
> +
> +static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg,
> +				       u64 *cur_tsc)
> +{
> +	return U64_MAX;
> +}
> +#endif /* CONFIG_HYPERV_TSCPAGE */
> +
>  #endif

With the (theoretical) question above answered,

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>

-- 
Vitaly

RE: [PATCH v3 2/2] Drivers: hv: Move Hyper-V clocksource code to new clocksource driver

[Michael Kelley]

From: Vitaly Kuznetsov <vkuznets@redhat.com> Sent: Thursday, May 30, 2019 2:48 AM
> > +		/*
> > +		 * sched_clock_register is needed on ARM64 but
> > +		 * is a no-op on x86
> > +		 */
> > +		sched_clock_register(read_hv_sched_clock_msr,
> > +						64, HV_CLOCK_HZ);
> 
> I'm not sure about ARM, but MSR-based clocksource would be a really bad
> choice for sched clock on x86, this will slow things down
> significantly. Luckily, as you're validly stating above,
> sched_clock_register() is a no-op on x86 as we don't define
> CONFIG_GENERIC_SCHED_CLOCK.
> 
> Can we actually *not* do sched_clock_register() in case
> TSC page is unavailable (and revert to counting jiffies or whatever)?
> 

We can't skip the sched_clock_register() on ARM64 because it
does define CONFIG_GENERIC_SCHED_CLOCK.  However, Hyper-V
should always provide REFERENCE_TSC_AVAILALBE on ARM64,
so we should never end up in the MSR-based code on ARM64.
Arguably that means the call to sched_clock_register() could be
removed since it's a no-op on x86.  But I'd like to keep it for symmetry
and in case there's a testing/debugging situation on ARM64 where
we want to clear REFERENCE_TSC_AVAILABLE and go down the
MSR-based code path.

Michael

RE: [PATCH v3 2/2] Drivers: hv: Move Hyper-V clocksource code to new clocksource driver

[Vitaly Kuznetsov]

Michael Kelley <mikelley@microsoft.com> writes:

> From: Vitaly Kuznetsov <vkuznets@redhat.com> Sent: Thursday, May 30, 2019 2:48 AM
>> > +		/*
>> > +		 * sched_clock_register is needed on ARM64 but
>> > +		 * is a no-op on x86
>> > +		 */
>> > +		sched_clock_register(read_hv_sched_clock_msr,
>> > +						64, HV_CLOCK_HZ);
>> 
>> I'm not sure about ARM, but MSR-based clocksource would be a really bad
>> choice for sched clock on x86, this will slow things down
>> significantly. Luckily, as you're validly stating above,
>> sched_clock_register() is a no-op on x86 as we don't define
>> CONFIG_GENERIC_SCHED_CLOCK.
>> 
>> Can we actually *not* do sched_clock_register() in case
>> TSC page is unavailable (and revert to counting jiffies or whatever)?
>> 
>
> We can't skip the sched_clock_register() on ARM64 because it
> does define CONFIG_GENERIC_SCHED_CLOCK.  However, Hyper-V
> should always provide REFERENCE_TSC_AVAILALBE on ARM64,
> so we should never end up in the MSR-based code on ARM64.
> Arguably that means the call to sched_clock_register() could be
> removed since it's a no-op on x86.  But I'd like to keep it for symmetry
> and in case there's a testing/debugging situation on ARM64 where
> we want to clear REFERENCE_TSC_AVAILABLE and go down the
> MSR-based code path.

Ok, so it is just a fall-back and not going to be actively used. Thanks!

-- 
Vitaly

Re: [PATCH v3 0/2] Drivers: hv: Move Hyper-V clock/timer code to separate clocksource driver

[Sasha Levin]

On Mon, May 27, 2019 at 02:59:07PM +0000, Michael Kelley wrote:
>This patch series moves Hyper-V clock/timer code to a separate Hyper-V
>clocksource driver. Previously, Hyper-V clock/timer code and data
>structures were mixed in with other Hyper-V code in the ISA independent
>drivers/hv code as well as in arch dependent code. The new Hyper-V
>clocksource driver is ISA independent, with a just few dependencies on
>arch specific functions. The patch series does not change any behavior
>or functionality -- it only reorganizes the existing code and fixes up
>the linkages. A few places outside of Hyper-V code are fixed up to use
>the new #include file structure.
>
>This restructuring is in response to Marc Zyngier's review comments
>on supporting Hyper-V running on ARM64, and is a good idea in general.
>It increases the amount of code shared between the x86 and ARM64
>architectures, and reduces the size of the new code for supporting
>Hyper-V on ARM64. A new version of the Hyper-V on ARM64 patches will
>follow once this clocksource restructuring is accepted.
>
>The code is diff'ed against Linux 5.2.0-rc1-next-20190524.
>
>Changes in v3:
>* Removed boolean argument to hv_init_clocksource(). Always call
>sched_clock_register, which is needed on ARM64 but a no-op on x86.
>* Removed separate cpuhp setup in hv_stimer_alloc() and instead
>directly call hv_stimer_init() and hv_stimer_cleanup() from
>corresponding VMbus functions.  This more closely matches original
>code and avoids clocksource stop/restart problems on ARM64 when
>VMbus code denies CPU offlining request.
>
>Changes in v2:
>* Revised commit short descriptions so the distinction between
>the first and second patches is clearer [GregKH]
>* Renamed new clocksource driver files and functions to use
>existing "timer" and "stimer" names instead of introducing
>"syntimer". [Vitaly Kuznetsov]
>* Introduced CONFIG_HYPER_TIMER to fix build problem when
>CONFIG_HYPERV=m [Vitaly Kuznetsov]
>* Added "Suggested-by: Marc Zyngier"
>
>Michael Kelley (2):
>  Drivers: hv: Create Hyper-V clocksource driver from existing
>    clockevents code
>  Drivers: hv: Move Hyper-V clocksource code to new clocksource driver
>
> MAINTAINERS                          |   2 +
> arch/x86/entry/vdso/vclock_gettime.c |   1 +
> arch/x86/entry/vdso/vma.c            |   2 +-
> arch/x86/hyperv/hv_init.c            |  91 +---------
> arch/x86/include/asm/hyperv-tlfs.h   |   6 +
> arch/x86/include/asm/mshyperv.h      |  81 ++-------
> arch/x86/kernel/cpu/mshyperv.c       |   2 +
> arch/x86/kvm/x86.c                   |   1 +
> drivers/clocksource/Makefile         |   1 +
> drivers/clocksource/hyperv_timer.c   | 321 +++++++++++++++++++++++++++++++++++
> drivers/hv/Kconfig                   |   3 +
> drivers/hv/hv.c                      | 156 +----------------
> drivers/hv/hv_util.c                 |   1 +
> drivers/hv/hyperv_vmbus.h            |   3 -
> drivers/hv/vmbus_drv.c               |  42 ++---
> include/clocksource/hyperv_timer.h   | 105 ++++++++++++
> 16 files changed, 484 insertions(+), 334 deletions(-)
> create mode 100644 drivers/clocksource/hyperv_timer.c
> create mode 100644 include/clocksource/hyperv_timer.h

Queued for hyperv-next, thanks!

--
Thanks,
Sasha