s390/time: 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.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Tested-by: Michael Kelley <mikelley@microsoft.com>  # Hyper-V
Link: https://lore.kernel.org/r/20230519102715.570170436@infradead.org

diff --git a/arch/s390/include/asm/timex.h b/arch/s390/include/asm/timex.h
index ce878e8..4d64665 100644 (file)
--- a/arch/s390/include/asm/timex.h
+++ b/arch/s390/include/asm/timex.h
@@ -63,7 +63,7 @@ static inline int store_tod_clock_ext_cc(union tod_clock *clk)
        return cc;
 }
 
-static inline void store_tod_clock_ext(union tod_clock *tod)
+static __always_inline void store_tod_clock_ext(union tod_clock *tod)
 {
        asm volatile("stcke %0" : "=Q" (*tod) : : "cc");
 }
@@ -177,7 +177,7 @@ static inline void local_tick_enable(unsigned long comp)
 
 typedef unsigned long cycles_t;
 
-static inline unsigned long get_tod_clock(void)
+static __always_inline unsigned long get_tod_clock(void)
 {
        union tod_clock clk;
 
@@ -204,6 +204,11 @@ void init_cpu_timer(void);
 
 extern union tod_clock tod_clock_base;
 
+static __always_inline unsigned long __get_tod_clock_monotonic(void)
+{
+       return get_tod_clock() - tod_clock_base.tod;
+}
+
 /**
  * get_clock_monotonic - returns current time in clock rate units
  *
@@ -216,7 +221,7 @@ static inline unsigned long get_tod_clock_monotonic(void)
        unsigned long tod;
 
        preempt_disable_notrace();
-       tod = get_tod_clock() - tod_clock_base.tod;
+       tod = __get_tod_clock_monotonic();
        preempt_enable_notrace();
        return tod;
 }
@@ -240,7 +245,7 @@ static inline unsigned long get_tod_clock_monotonic(void)
  * -> ns = (th * 125) + ((tl * 125) >> 9);
  *
  */
-static inline unsigned long tod_to_ns(unsigned long todval)
+static __always_inline unsigned long tod_to_ns(unsigned long todval)
 {
        return ((todval >> 9) * 125) + (((todval & 0x1ff) * 125) >> 9);
 }

diff --git a/arch/s390/kernel/time.c b/arch/s390/kernel/time.c
index 6b7b6d5..2762781 100644 (file)
--- a/arch/s390/kernel/time.c
+++ b/arch/s390/kernel/time.c
@@ -102,6 +102,11 @@ void __init time_early_init(void)
                        ((long) qui.old_leap * 4096000000L);
 }
 
+unsigned long long noinstr sched_clock_noinstr(void)
+{
+       return tod_to_ns(__get_tod_clock_monotonic());
+}
+
 /*
  * Scheduler clock - returns current time in nanosec units.
  */