From 5c5e9a2b25b6a79d4b7a5f2a54d02ef1c36dc35a Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 19 May 2023 12:21:09 +0200 Subject: x86/tsc: Provide sched_clock_noinstr() With the intent to provide local_clock_noinstr(), a variant of local_clock() that's safe to be called from noinstr code (with the assumption that any such code will already be non-preemptible), prepare for things by providing a noinstr sched_clock_noinstr() function. Specifically, preempt_enable_*() calls out to schedule(), which upsets noinstr validation efforts. vmlinux.o: warning: objtool: native_sched_clock+0x96: call to preempt_schedule_notrace_thunk() leaves .noinstr.text section vmlinux.o: warning: objtool: kvm_clock_read+0x22: call to preempt_schedule_notrace_thunk() leaves .noinstr.text section Signed-off-by: Peter Zijlstra (Intel) Tested-by: Michael Kelley # Hyper-V Link: https://lore.kernel.org/r/20230519102715.910937674@infradead.org --- arch/x86/kernel/kvmclock.c | 4 ++-- arch/x86/kernel/tsc.c | 38 +++++++++++++++++++++++++++++--------- arch/x86/xen/time.c | 3 +-- 3 files changed, 32 insertions(+), 13 deletions(-) diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c index 0f35d44c56fe..fb8f52149be9 100644 --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -71,7 +71,7 @@ static int kvm_set_wallclock(const struct timespec64 *now) return -ENODEV; } -static noinstr u64 kvm_clock_read(void) +static u64 kvm_clock_read(void) { u64 ret; @@ -88,7 +88,7 @@ static u64 kvm_clock_get_cycles(struct clocksource *cs) static noinstr u64 kvm_sched_clock_read(void) { - return kvm_clock_read() - kvm_sched_clock_offset; + return pvclock_clocksource_read_nowd(this_cpu_pvti()) - kvm_sched_clock_offset; } static inline void kvm_sched_clock_init(bool stable) diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 344698852146..782a90ed1a0d 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -69,12 +69,10 @@ static int __init tsc_early_khz_setup(char *buf) } early_param("tsc_early_khz", tsc_early_khz_setup); -__always_inline void cyc2ns_read_begin(struct cyc2ns_data *data) +__always_inline void __cyc2ns_read(struct cyc2ns_data *data) { int seq, idx; - preempt_disable_notrace(); - do { seq = this_cpu_read(cyc2ns.seq.seqcount.sequence); idx = seq & 1; @@ -86,6 +84,12 @@ __always_inline void cyc2ns_read_begin(struct cyc2ns_data *data) } while (unlikely(seq != this_cpu_read(cyc2ns.seq.seqcount.sequence))); } +__always_inline void cyc2ns_read_begin(struct cyc2ns_data *data) +{ + preempt_disable_notrace(); + __cyc2ns_read(data); +} + __always_inline void cyc2ns_read_end(void) { preempt_enable_notrace(); @@ -115,18 +119,25 @@ __always_inline void cyc2ns_read_end(void) * -johnstul@us.ibm.com "math is hard, lets go shopping!" */ -static __always_inline unsigned long long cycles_2_ns(unsigned long long cyc) +static __always_inline unsigned long long __cycles_2_ns(unsigned long long cyc) { struct cyc2ns_data data; unsigned long long ns; - cyc2ns_read_begin(&data); + __cyc2ns_read(&data); ns = data.cyc2ns_offset; ns += mul_u64_u32_shr(cyc, data.cyc2ns_mul, data.cyc2ns_shift); - cyc2ns_read_end(); + return ns; +} +static __always_inline unsigned long long cycles_2_ns(unsigned long long cyc) +{ + unsigned long long ns; + preempt_disable_notrace(); + ns = __cycles_2_ns(cyc); + preempt_enable_notrace(); return ns; } @@ -223,7 +234,7 @@ noinstr u64 native_sched_clock(void) u64 tsc_now = rdtsc(); /* return the value in ns */ - return cycles_2_ns(tsc_now); + return __cycles_2_ns(tsc_now); } /* @@ -250,7 +261,7 @@ u64 native_sched_clock_from_tsc(u64 tsc) /* We need to define a real function for sched_clock, to override the weak default version */ #ifdef CONFIG_PARAVIRT -noinstr u64 sched_clock(void) +noinstr u64 sched_clock_noinstr(void) { return paravirt_sched_clock(); } @@ -260,11 +271,20 @@ bool using_native_sched_clock(void) return static_call_query(pv_sched_clock) == native_sched_clock; } #else -u64 sched_clock(void) __attribute__((alias("native_sched_clock"))); +u64 sched_clock_noinstr(void) __attribute__((alias("native_sched_clock"))); bool using_native_sched_clock(void) { return true; } #endif +notrace u64 sched_clock(void) +{ + u64 now; + preempt_disable_notrace(); + now = sched_clock_noinstr(); + preempt_enable_notrace(); + return now; +} + int check_tsc_unstable(void) { return tsc_unstable; diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c index b74ac2562cfb..52fa5609b7f6 100644 --- a/arch/x86/xen/time.c +++ b/arch/x86/xen/time.c @@ -66,11 +66,10 @@ static noinstr u64 xen_sched_clock(void) struct pvclock_vcpu_time_info *src; u64 ret; - preempt_disable_notrace(); src = &__this_cpu_read(xen_vcpu)->time; ret = pvclock_clocksource_read_nowd(src); ret -= xen_sched_clock_offset; - preempt_enable_notrace(); + return ret; } -- cgit v1.2.3