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Message-ID: <20230123205515.118011340@infradead.org>
Date: Mon, 23 Jan 2023 21:50:13 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: mingo@...nel.org
Cc: will@...nel.org, peterz@...radead.org, boqun.feng@...il.com,
mark.rutland@....com, tglx@...utronix.de, bp@...en8.de,
dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
seanjc@...gle.com, pbonzini@...hat.com, jgross@...e.com,
srivatsa@...il.mit.edu, amakhalov@...are.com,
pv-drivers@...are.com, rostedt@...dmis.org, mhiramat@...nel.org,
wanpengli@...cent.com, vkuznets@...hat.com,
boris.ostrovsky@...cle.com, rafael@...nel.org,
daniel.lezcano@...aro.org, juri.lelli@...hat.com,
vincent.guittot@...aro.org, dietmar.eggemann@....com,
bsegall@...gle.com, mgorman@...e.de, bristot@...hat.com,
vschneid@...hat.com, linux-kernel@...r.kernel.org,
kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
linux-trace-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: [PATCH 4/6] x86: Mark sched_clock() noinstr
In order to use sched_clock() from noinstr code, mark it and all it's
implenentations noinstr.
The whole pvclock thing (used by KVM/Xen) is a bit of a pain,
since it calls out to watchdogs, create a
pvclock_clocksource_read_nowd() variant doesn't do that and can be
noinstr.
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
arch/x86/include/asm/kvmclock.h | 2 +-
arch/x86/include/asm/paravirt.h | 2 +-
arch/x86/include/asm/pvclock.h | 3 ++-
arch/x86/kernel/cpu/vmware.c | 2 +-
arch/x86/kernel/kvmclock.c | 6 +++---
arch/x86/kernel/pvclock.c | 19 +++++++++++++++----
arch/x86/kernel/tsc.c | 7 +++----
arch/x86/xen/time.c | 12 ++++++++++--
include/linux/math64.h | 4 ++--
9 files changed, 38 insertions(+), 19 deletions(-)
--- a/arch/x86/include/asm/kvmclock.h
+++ b/arch/x86/include/asm/kvmclock.h
@@ -8,7 +8,7 @@ extern struct clocksource kvm_clock;
DECLARE_PER_CPU(struct pvclock_vsyscall_time_info *, hv_clock_per_cpu);
-static inline struct pvclock_vcpu_time_info *this_cpu_pvti(void)
+static __always_inline struct pvclock_vcpu_time_info *this_cpu_pvti(void)
{
return &this_cpu_read(hv_clock_per_cpu)->pvti;
}
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -26,7 +26,7 @@ DECLARE_STATIC_CALL(pv_sched_clock, dumm
void paravirt_set_sched_clock(u64 (*func)(void));
-static inline u64 paravirt_sched_clock(void)
+static __always_inline u64 paravirt_sched_clock(void)
{
return static_call(pv_sched_clock)();
}
--- a/arch/x86/include/asm/pvclock.h
+++ b/arch/x86/include/asm/pvclock.h
@@ -7,6 +7,7 @@
/* some helper functions for xen and kvm pv clock sources */
u64 pvclock_clocksource_read(struct pvclock_vcpu_time_info *src);
+u64 pvclock_clocksource_read_nowd(struct pvclock_vcpu_time_info *src);
u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src);
void pvclock_set_flags(u8 flags);
unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src);
@@ -39,7 +40,7 @@ bool pvclock_read_retry(const struct pvc
* Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction,
* yielding a 64-bit result.
*/
-static inline u64 pvclock_scale_delta(u64 delta, u32 mul_frac, int shift)
+static __always_inline u64 pvclock_scale_delta(u64 delta, u32 mul_frac, int shift)
{
u64 product;
#ifdef __i386__
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -143,7 +143,7 @@ static __init int parse_no_stealacc(char
}
early_param("no-steal-acc", parse_no_stealacc);
-static unsigned long long notrace vmware_sched_clock(void)
+static noinstr u64 vmware_sched_clock(void)
{
unsigned long long ns;
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -71,12 +71,12 @@ static int kvm_set_wallclock(const struc
return -ENODEV;
}
-static u64 kvm_clock_read(void)
+static noinstr u64 kvm_clock_read(void)
{
u64 ret;
preempt_disable_notrace();
- ret = pvclock_clocksource_read(this_cpu_pvti());
+ ret = pvclock_clocksource_read_nowd(this_cpu_pvti());
preempt_enable_notrace();
return ret;
}
@@ -86,7 +86,7 @@ static u64 kvm_clock_get_cycles(struct c
return kvm_clock_read();
}
-static u64 kvm_sched_clock_read(void)
+static noinstr u64 kvm_sched_clock_read(void)
{
return kvm_clock_read() - kvm_sched_clock_offset;
}
--- a/arch/x86/kernel/pvclock.c
+++ b/arch/x86/kernel/pvclock.c
@@ -64,7 +64,8 @@ u8 pvclock_read_flags(struct pvclock_vcp
return flags & valid_flags;
}
-u64 pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
+static __always_inline
+u64 __pvclock_clocksource_read(struct pvclock_vcpu_time_info *src, bool dowd)
{
unsigned version;
u64 ret;
@@ -77,7 +78,7 @@ u64 pvclock_clocksource_read(struct pvcl
flags = src->flags;
} while (pvclock_read_retry(src, version));
- if (unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) {
+ if (dowd && unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) {
src->flags &= ~PVCLOCK_GUEST_STOPPED;
pvclock_touch_watchdogs();
}
@@ -100,15 +101,25 @@ u64 pvclock_clocksource_read(struct pvcl
* updating at the same time, and one of them could be slightly behind,
* making the assumption that last_value always go forward fail to hold.
*/
- last = atomic64_read(&last_value);
+ last = arch_atomic64_read(&last_value);
do {
if (ret <= last)
return last;
- } while (!atomic64_try_cmpxchg(&last_value, &last, ret));
+ } while (!arch_atomic64_try_cmpxchg(&last_value, &last, ret));
return ret;
}
+u64 pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
+{
+ return __pvclock_clocksource_read(src, true);
+}
+
+noinstr u64 pvclock_clocksource_read_nowd(struct pvclock_vcpu_time_info *src)
+{
+ return __pvclock_clocksource_read(src, false);
+}
+
void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock,
struct pvclock_vcpu_time_info *vcpu_time,
struct timespec64 *ts)
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -215,7 +215,7 @@ static void __init cyc2ns_init_secondary
/*
* Scheduler clock - returns current time in nanosec units.
*/
-u64 native_sched_clock(void)
+noinstr u64 native_sched_clock(void)
{
if (static_branch_likely(&__use_tsc)) {
u64 tsc_now = rdtsc();
@@ -248,7 +248,7 @@ 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
-unsigned long long sched_clock(void)
+noinstr u64 sched_clock(void)
{
return paravirt_sched_clock();
}
@@ -258,8 +258,7 @@ bool using_native_sched_clock(void)
return static_call_query(pv_sched_clock) == native_sched_clock;
}
#else
-unsigned long long
-sched_clock(void) __attribute__((alias("native_sched_clock")));
+u64 sched_clock(void) __attribute__((alias("native_sched_clock")));
bool using_native_sched_clock(void) { return true; }
#endif
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -60,9 +60,17 @@ static u64 xen_clocksource_get_cycles(st
return xen_clocksource_read();
}
-static u64 xen_sched_clock(void)
+static noinstr u64 xen_sched_clock(void)
{
- return xen_clocksource_read() - xen_sched_clock_offset;
+ 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;
}
static void xen_read_wallclock(struct timespec64 *ts)
--- a/include/linux/math64.h
+++ b/include/linux/math64.h
@@ -161,7 +161,7 @@ static inline u64 mul_u32_u32(u32 a, u32
#if defined(CONFIG_ARCH_SUPPORTS_INT128) && defined(__SIZEOF_INT128__)
#ifndef mul_u64_u32_shr
-static inline u64 mul_u64_u32_shr(u64 a, u32 mul, unsigned int shift)
+static __always_inline u64 mul_u64_u32_shr(u64 a, u32 mul, unsigned int shift)
{
return (u64)(((unsigned __int128)a * mul) >> shift);
}
@@ -177,7 +177,7 @@ static inline u64 mul_u64_u64_shr(u64 a,
#else
#ifndef mul_u64_u32_shr
-static inline u64 mul_u64_u32_shr(u64 a, u32 mul, unsigned int shift)
+static __always_inline u64 mul_u64_u32_shr(u64 a, u32 mul, unsigned int shift)
{
u32 ah, al;
u64 ret;
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