Commit-ID: fd1fea6834d0f9f93062ae6685862908a9baed39 Gitweb: https://git.kernel.org/tip/fd1fea6834d0f9f93062ae6685862908a9baed39 Author: Michael Kelley mikelley@microsoft.com AuthorDate: Mon, 1 Jul 2019 04:25:56 +0000 Committer: Thomas Gleixner tglx@linutronix.de CommitDate: Wed, 3 Jul 2019 11:00:59 +0200

clocksource/drivers: Make Hyper-V clocksource ISA agnostic

Hyper-V clock/timer code and data structures are currently mixed in with other code in the ISA independent drivers/hv directory as well as the ISA dependent Hyper-V code under arch/x86.

Consolidate this code and data structures into a Hyper-V clocksource driver to better follow the Linux model. In doing so, separate out the ISA dependent portions so the new clocksource driver works for x86 and for the in-process Hyper-V on ARM64 code.

To start, move the existing clockevents code to create the new clocksource driver. 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 Signed-off-by: Thomas Gleixner tglx@linutronix.de Reviewed-by: Vitaly Kuznetsov vkuznets@redhat.com Cc: "bp@alien8.de" bp@alien8.de Cc: "will.deacon@arm.com" will.deacon@arm.com Cc: "catalin.marinas@arm.com" catalin.marinas@arm.com Cc: "mark.rutland@arm.com" mark.rutland@arm.com Cc: "linux-arm-kernel@lists.infradead.org" linux-arm-kernel@lists.infradead.org Cc: "gregkh@linuxfoundation.org" gregkh@linuxfoundation.org Cc: "linux-hyperv@vger.kernel.org" linux-hyperv@vger.kernel.org Cc: "olaf@aepfle.de" olaf@aepfle.de Cc: "apw@canonical.com" apw@canonical.com Cc: "jasowang@redhat.com" jasowang@redhat.com Cc: "marcelo.cerri@canonical.com" marcelo.cerri@canonical.com Cc: Sunil Muthuswamy sunilmut@microsoft.com Cc: KY Srinivasan kys@microsoft.com Cc: "sashal@kernel.org" sashal@kernel.org Cc: "vincenzo.frascino@arm.com" vincenzo.frascino@arm.com Cc: "linux-arch@vger.kernel.org" linux-arch@vger.kernel.org Cc: "linux-mips@vger.kernel.org" linux-mips@vger.kernel.org Cc: "linux-kselftest@vger.kernel.org" linux-kselftest@vger.kernel.org Cc: "arnd@arndb.de" arnd@arndb.de Cc: "linux@armlinux.org.uk" linux@armlinux.org.uk Cc: "ralf@linux-mips.org" ralf@linux-mips.org Cc: "paul.burton@mips.com" paul.burton@mips.com Cc: "daniel.lezcano@linaro.org" daniel.lezcano@linaro.org Cc: "salyzyn@android.com" salyzyn@android.com Cc: "pcc@google.com" pcc@google.com Cc: "shuah@kernel.org" shuah@kernel.org Cc: "0x7f454c46@gmail.com" 0x7f454c46@gmail.com Cc: "linux@rasmusvillemoes.dk" linux@rasmusvillemoes.dk Cc: "huw@codeweavers.com" huw@codeweavers.com Cc: "sfr@canb.auug.org.au" sfr@canb.auug.org.au Cc: "pbonzini@redhat.com" pbonzini@redhat.com Cc: "rkrcmar@redhat.com" rkrcmar@redhat.com Cc: "kvm@vger.kernel.org" kvm@vger.kernel.org Link: https://lkml.kernel.org/r/1561955054-1838-2-git-send-email-mikelley@microsof...

--- MAINTAINERS | 2 + arch/x86/include/asm/hyperv-tlfs.h | 6 ++ arch/x86/kernel/cpu/mshyperv.c | 4 +- drivers/clocksource/Makefile | 1 + drivers/clocksource/hyperv_timer.c | 200 +++++++++++++++++++++++++++++++++++++ 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, 268 insertions(+), 176 deletions(-)

diff --git a/MAINTAINERS b/MAINTAINERS index a2812972b7b0..bfde42a76a95 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -7313,6 +7313,7 @@ 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 @@ -7323,6 +7324,7 @@ 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 cdf44aa9a501..af78cd72b8f3 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 7df29f08871b..1e5f7a03ddf5 100644 --- a/arch/x86/kernel/cpu/mshyperv.c +++ b/arch/x86/kernel/cpu/mshyperv.c @@ -17,6 +17,7 @@ #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> @@ -80,6 +81,7 @@ __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(); @@ -89,7 +91,7 @@ __visible void __irq_entry hv_stimer0_vector_handler(struct pt_regs *regs) int hv_setup_stimer0_irq(int *irq, int *vector, void (*handler)(void)) { *vector = HYPERV_STIMER0_VECTOR; - *irq = 0; /* Unused on x86/x64 */ + *irq = -1; /* Unused on x86/x64 */ hv_stimer0_handler = handler; return 0; } diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile index 5582252efb31..2e7936e7833f 100644 --- a/drivers/clocksource/Makefile +++ b/drivers/clocksource/Makefile @@ -86,3 +86,4 @@ 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 000000000000..68a28af31561 --- /dev/null +++ b/drivers/clocksource/hyperv_timer.c @@ -0,0 +1,200 @@ +// 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; + + 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 + */ +void hv_stimer_init(unsigned int cpu) +{ + struct clock_event_device *ce; + + /* + * Synthetic timers are always available except on old versions of + * Hyper-V on x86. In that case, just return as Linux will use a + * clocksource based on emulated PIT or LAPIC timer hardware. + */ + if (!(ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE)) + return; + + 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); +} +EXPORT_SYMBOL_GPL(hv_stimer_init); + +/* + * hv_stimer_cleanup - Per-cpu cleanup of the clockevent + */ +void 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); + hv_ce_shutdown(ce); + } +} +EXPORT_SYMBOL_GPL(hv_stimer_cleanup); + +/* hv_stimer_alloc - Global initialization of the clockevent and stimer0 */ +int hv_stimer_alloc(int sint) +{ + int ret; + + 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) { + ret = hv_setup_stimer0_irq(&stimer0_irq, &stimer0_vector, + hv_stimer0_isr); + if (ret) { + free_percpu(hv_clock_event); + hv_clock_event = NULL; + return ret; + } + } + + 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 && (stimer0_irq != 0)) { + hv_remove_stimer0_irq(stimer0_irq); + stimer0_irq = 0; + } + free_percpu(hv_clock_event); + hv_clock_event = NULL; +} +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 1c1a2514d6f3..c423e57ae888 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 a1ea482183e8..6188fb7dda42 100644 --- a/drivers/hv/hv.c +++ b/drivers/hv/hv.c @@ -16,27 +16,13 @@ #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"

/* The one and only */ 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. * @@ -47,9 +33,6 @@ 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; }

@@ -88,89 +71,6 @@ 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; @@ -199,14 +99,6 @@ 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) { @@ -229,11 +121,6 @@ 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: /* @@ -252,7 +139,6 @@ 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); @@ -311,36 +197,9 @@ 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; }

/* @@ -388,14 +247,7 @@ 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 b8e1ff05f110..362e70e9d145 100644 --- a/drivers/hv/hyperv_vmbus.h +++ b/drivers/hv/hyperv_vmbus.h @@ -138,7 +138,6 @@ 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 { @@ -176,8 +175,6 @@ extern int hv_synic_init(unsigned int cpu);

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 92b1874b3eb3..72d5a7cde7ea 100644 --- a/drivers/hv/vmbus_drv.c +++ b/drivers/hv/vmbus_drv.c @@ -30,6 +30,7 @@ #include <linux/kdebug.h> #include <linux/efi.h> #include <linux/random.h> +#include <clocksource/hyperv_timer.h> #include "hyperv_vmbus.h"

struct vmbus_dynid { @@ -955,17 +956,6 @@ 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; @@ -1159,9 +1149,10 @@ 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); }

@@ -1263,14 +1254,19 @@ 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(); @@ -1318,6 +1314,8 @@ 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(); @@ -2064,7 +2062,7 @@ static struct acpi_driver vmbus_acpi_driver = {

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 */ @@ -2075,6 +2073,8 @@ 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, @@ -2082,7 +2082,9 @@ 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(); };

@@ -2131,7 +2133,7 @@ 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 000000000000..0cd73f7bc992 --- /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 void hv_stimer_init(unsigned int cpu); +extern void hv_stimer_cleanup(unsigned int cpu); +extern void hv_stimer_global_cleanup(void); +extern void hv_stimer0_isr(void); + +#endif

Commit-ID: dd2cb348613b44f9d948b068775e159aad298599 Gitweb: https://git.kernel.org/tip/dd2cb348613b44f9d948b068775e159aad298599 Author: Michael Kelley mikelley@microsoft.com AuthorDate: Mon, 1 Jul 2019 04:26:06 +0000 Committer: Thomas Gleixner tglx@linutronix.de CommitDate: Wed, 3 Jul 2019 11:00:59 +0200

clocksource/drivers: Continue making Hyper-V clocksource ISA agnostic

Continue consolidating Hyper-V clock and timer code into an ISA independent Hyper-V clocksource driver.

Move the existing clocksource code under drivers/hv and arch/x86 to the new clocksource driver while separating out the ISA dependencies. Update Hyper-V initialization to call initialization and cleanup routines since the Hyper-V synthetic clock is not independently enumerated in ACPI.

Update Hyper-V clocksource users in KVM and VDSO to get definitions from the 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 Signed-off-by: Thomas Gleixner tglx@linutronix.de Reviewed-by: Vitaly Kuznetsov vkuznets@redhat.com Cc: "bp@alien8.de" bp@alien8.de Cc: "will.deacon@arm.com" will.deacon@arm.com Cc: "catalin.marinas@arm.com" catalin.marinas@arm.com Cc: "mark.rutland@arm.com" mark.rutland@arm.com Cc: "linux-arm-kernel@lists.infradead.org" linux-arm-kernel@lists.infradead.org Cc: "gregkh@linuxfoundation.org" gregkh@linuxfoundation.org Cc: "linux-hyperv@vger.kernel.org" linux-hyperv@vger.kernel.org Cc: "olaf@aepfle.de" olaf@aepfle.de Cc: "apw@canonical.com" apw@canonical.com Cc: "jasowang@redhat.com" jasowang@redhat.com Cc: "marcelo.cerri@canonical.com" marcelo.cerri@canonical.com Cc: Sunil Muthuswamy sunilmut@microsoft.com Cc: KY Srinivasan kys@microsoft.com Cc: "sashal@kernel.org" sashal@kernel.org Cc: "vincenzo.frascino@arm.com" vincenzo.frascino@arm.com Cc: "linux-arch@vger.kernel.org" linux-arch@vger.kernel.org Cc: "linux-mips@vger.kernel.org" linux-mips@vger.kernel.org Cc: "linux-kselftest@vger.kernel.org" linux-kselftest@vger.kernel.org Cc: "arnd@arndb.de" arnd@arndb.de Cc: "linux@armlinux.org.uk" linux@armlinux.org.uk Cc: "ralf@linux-mips.org" ralf@linux-mips.org Cc: "paul.burton@mips.com" paul.burton@mips.com Cc: "daniel.lezcano@linaro.org" daniel.lezcano@linaro.org Cc: "salyzyn@android.com" salyzyn@android.com Cc: "pcc@google.com" pcc@google.com Cc: "shuah@kernel.org" shuah@kernel.org Cc: "0x7f454c46@gmail.com" 0x7f454c46@gmail.com Cc: "linux@rasmusvillemoes.dk" linux@rasmusvillemoes.dk Cc: "huw@codeweavers.com" huw@codeweavers.com Cc: "sfr@canb.auug.org.au" sfr@canb.auug.org.au Cc: "pbonzini@redhat.com" pbonzini@redhat.com Cc: "rkrcmar@redhat.com" rkrcmar@redhat.com Cc: "kvm@vger.kernel.org" kvm@vger.kernel.org Link: https://lkml.kernel.org/r/1561955054-1838-3-git-send-email-mikelley@microsof...

--- arch/x86/entry/vdso/vma.c | 2 +- arch/x86/hyperv/hv_init.c | 91 +------------------- arch/x86/include/asm/mshyperv.h | 81 +++--------------- arch/x86/include/asm/vdso/gettimeofday.h | 2 +- arch/x86/kvm/x86.c | 1 + drivers/clocksource/hyperv_timer.c | 139 +++++++++++++++++++++++++++++++ drivers/hv/hv_util.c | 1 + include/clocksource/hyperv_timer.h | 80 ++++++++++++++++++ 8 files changed, 237 insertions(+), 160 deletions(-)

diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c index 8db1f594e8b1..349a61d8bf34 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 1608050e9df9..0e033ef11a9f 100644 --- a/arch/x86/hyperv/hv_init.c +++ b/arch/x86/hyperv/hv_init.c @@ -17,64 +17,13 @@ #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); @@ -343,42 +292,8 @@ 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 cc60e617931c..f4fa8a9d5d0b 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/include/asm/vdso/gettimeofday.h b/arch/x86/include/asm/vdso/gettimeofday.h index a14039a59abd..ae91429129a6 100644 --- a/arch/x86/include/asm/vdso/gettimeofday.h +++ b/arch/x86/include/asm/vdso/gettimeofday.h @@ -18,7 +18,7 @@ #include <asm/unistd.h> #include <asm/msr.h> #include <asm/pvclock.h> -#include <asm/mshyperv.h> +#include <clocksource/hyperv_timer.h>

#define __vdso_data (VVAR(_vdso_data))

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 8ec676029365..5e1db26b5e15 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -67,6 +67,7 @@ #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 68a28af31561..ba2c79e6a0ee 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> @@ -198,3 +200,140 @@ 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 notrace 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 notrace 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, +}; + +#ifdef CONFIG_HYPERV_TSCPAGE +static bool __init hv_init_tsc_clocksource(void) +{ + u64 tsc_msr; + phys_addr_t phys_addr; + + if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE)) + return false; + + tsc_pg = vmalloc(PAGE_SIZE); + if (!tsc_pg) + return false; + + 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 true; +} +#else +static bool __init hv_init_tsc_clocksource(void) +{ + return false; +} +#endif + + +void __init hv_init_clocksource(void) +{ + /* + * Try to set up the TSC page clocksource. If it succeeds, we're + * done. Otherwise, set up the MSR clocksoruce. At least one of + * these will always be available except on very old versions of + * Hyper-V on x86. In that case we won't have a Hyper-V + * clocksource, but Linux will still run with a clocksource based + * on the emulated PIT or LAPIC timer. + */ + if (hv_init_tsc_clocksource()) + return; + + if (!(ms_hyperv.features & HV_MSR_TIME_REF_COUNT_AVAILABLE)) + return; + + hyperv_cs = &hyperv_cs_msr; + 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 7d3d31f099ea..e32681ee7b9f 100644 --- a/drivers/hv/hv_util.c +++ b/drivers/hv/hv_util.c @@ -17,6 +17,7 @@ #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 0cd73f7bc992..a821deb8ecb2 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 +28,80 @@ extern void hv_stimer_cleanup(unsigned int cpu); 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 notrace 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 notrace 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