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clocksource/drivers/hyperv: Add Hyper-V specific sched clock function

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Hyper-V guests use the default native_sched_clock() in
pv_ops.time.sched_clock on x86. But native_sched_clock() directly uses the
raw TSC value, which can be discontinuous in a Hyper-V VM.
    
Add the generic hv_setup_sched_clock() to set the sched clock function
appropriately. On x86, this sets pv_ops.time.sched_clock to read the
Hyper-V reference TSC value that is scaled and adjusted to be continuous.
    
Also move the Hyper-V reference TSC initialization much earlier in the boot
process so no discontinuity is observed when pv_ops.time.sched_clock
calculates its offset.

[ tglx: Folded build fix ]

Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lkml.kernel.org/r/20190814123216.32245-3-Tianyu.Lan@microsoft.com
This commit is contained in:
Tianyu Lan 2019-08-14 20:32:16 +08:00 committed by Thomas Gleixner
parent adb87ff4f9
commit bd00cd52d5
4 changed files with 21 additions and 12 deletions
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2
arch/x86/hyperv/hv_init.c
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@ -301,8 +301,6 @@ void __init hyperv_init(void)
x86_init.pci.arch_init = hv_pci_init; x86_init.pci.arch_init = hv_pci_init;
/* Register Hyper-V specific clocksource */
hv_init_clocksource();
return; return;
remove_cpuhp_state: remove_cpuhp_state:

8
arch/x86/kernel/cpu/mshyperv.c
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@ -29,6 +29,7 @@
#include <asm/timer.h> #include <asm/timer.h>
#include <asm/reboot.h> #include <asm/reboot.h>
#include <asm/nmi.h> #include <asm/nmi.h>
#include <clocksource/hyperv_timer.h>
struct ms_hyperv_info ms_hyperv; struct ms_hyperv_info ms_hyperv;
EXPORT_SYMBOL_GPL(ms_hyperv); EXPORT_SYMBOL_GPL(ms_hyperv);
@ -338,9 +339,16 @@ static void __init ms_hyperv_init_platform(void)
x2apic_phys = 1; x2apic_phys = 1;
# endif # endif
/* Register Hyper-V specific clocksource */
hv_init_clocksource();
#endif #endif
} }
void hv_setup_sched_clock(void *sched_clock)
{
pv_ops.time.sched_clock = sched_clock;
}
const __initconst struct hypervisor_x86 x86_hyper_ms_hyperv = { const __initconst struct hypervisor_x86 x86_hyper_ms_hyperv = {
.name = "Microsoft Hyper-V", .name = "Microsoft Hyper-V",
.detect = ms_hyperv_platform, .detect = ms_hyperv_platform,

22
drivers/clocksource/hyperv_timer.c
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@ -22,6 +22,7 @@
#include <asm/mshyperv.h> #include <asm/mshyperv.h>
static struct clock_event_device __percpu *hv_clock_event; static struct clock_event_device __percpu *hv_clock_event;
static u64 hv_sched_clock_offset __ro_after_init;
/* /*
* If false, we're using the old mechanism for stimer0 interrupts * If false, we're using the old mechanism for stimer0 interrupts
@ -222,7 +223,7 @@ struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
} }
EXPORT_SYMBOL_GPL(hv_get_tsc_page); EXPORT_SYMBOL_GPL(hv_get_tsc_page);
static u64 notrace read_hv_sched_clock_tsc(void) static u64 notrace read_hv_clock_tsc(struct clocksource *arg)
{ {
u64 current_tick = hv_read_tsc_page(&tsc_pg); u64 current_tick = hv_read_tsc_page(&tsc_pg);
@ -232,9 +233,9 @@ static u64 notrace read_hv_sched_clock_tsc(void)
return current_tick; return current_tick;
} }
static u64 read_hv_clock_tsc(struct clocksource *arg) static u64 read_hv_sched_clock_tsc(void)
{ {
return read_hv_sched_clock_tsc(); return read_hv_clock_tsc(NULL) - hv_sched_clock_offset;
} }
static struct clocksource hyperv_cs_tsc = { static struct clocksource hyperv_cs_tsc = {
@ -246,7 +247,7 @@ static struct clocksource hyperv_cs_tsc = {
}; };
#endif #endif
static u64 notrace read_hv_sched_clock_msr(void) static u64 notrace read_hv_clock_msr(struct clocksource *arg)
{ {
u64 current_tick; u64 current_tick;
/* /*
@ -258,9 +259,9 @@ static u64 notrace read_hv_sched_clock_msr(void)
return current_tick; return current_tick;
} }
static u64 read_hv_clock_msr(struct clocksource *arg) static u64 read_hv_sched_clock_msr(void)
{ {
return read_hv_sched_clock_msr(); return read_hv_clock_msr(NULL) - hv_sched_clock_offset;
} }
static struct clocksource hyperv_cs_msr = { static struct clocksource hyperv_cs_msr = {
@ -298,8 +299,9 @@ static bool __init hv_init_tsc_clocksource(void)
hv_set_clocksource_vdso(hyperv_cs_tsc); hv_set_clocksource_vdso(hyperv_cs_tsc);
clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100); clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);
/* sched_clock_register is needed on ARM64 but is a no-op on x86 */ hv_sched_clock_offset = hyperv_cs->read(hyperv_cs);
sched_clock_register(read_hv_sched_clock_tsc, 64, HV_CLOCK_HZ); hv_setup_sched_clock(read_hv_sched_clock_tsc);
return true; return true;
} }
#else #else
@ -329,7 +331,7 @@ void __init hv_init_clocksource(void)
hyperv_cs = &hyperv_cs_msr; hyperv_cs = &hyperv_cs_msr;
clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100); clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);
/* sched_clock_register is needed on ARM64 but is a no-op on x86 */ hv_sched_clock_offset = hyperv_cs->read(hyperv_cs);
sched_clock_register(read_hv_sched_clock_msr, 64, HV_CLOCK_HZ); hv_setup_sched_clock(read_hv_sched_clock_msr);
} }
EXPORT_SYMBOL_GPL(hv_init_clocksource); EXPORT_SYMBOL_GPL(hv_init_clocksource);

1
include/asm-generic/mshyperv.h
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@ -167,6 +167,7 @@ void hyperv_report_panic(struct pt_regs *regs, long err);
void hyperv_report_panic_msg(phys_addr_t pa, size_t size); void hyperv_report_panic_msg(phys_addr_t pa, size_t size);
bool hv_is_hyperv_initialized(void); bool hv_is_hyperv_initialized(void);
void hyperv_cleanup(void); void hyperv_cleanup(void);
void hv_setup_sched_clock(void *sched_clock);
#else /* CONFIG_HYPERV */ #else /* CONFIG_HYPERV */
static inline bool hv_is_hyperv_initialized(void) { return false; } static inline bool hv_is_hyperv_initialized(void) { return false; }
static inline void hyperv_cleanup(void) {} static inline void hyperv_cleanup(void) {}