Switching between reading the virtual or physical counters is
problematic, as some core code wants a view of time before we're fully
set up. Using a function pointer and switching the source after the
first read can make time appear to go backwards, and having a check in
the read function is an unfortunate block on what we want to be a fast
path.
Instead, this patch makes us always use the virtual counters. If we're a
guest, or don't have hyp mode, we'll use the virtual timers, and as such
don't care about CNTVOFF as long as it doesn't change in such a way as
to make time appear to travel backwards. As the guest will use the
virtual timers, a (potential) KVM host must use the physical timers
(which can wake up the host even if they fire while a guest is
executing), and hence a host must have CNTVOFF set to zero so as to have
a consistent view of time between the physical timers and virtual
counters.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Cc: Rob Herring <rob.herring@calxeda.com>
-static inline u64 arch_counter_get_cntpct(void)
-{
- u64 cval;
-
- isb();
- asm volatile("mrrc p15, 0, %Q0, %R0, c14" : "=r" (cval));
- return cval;
-}
-
static inline u64 arch_counter_get_cntvct(void)
{
u64 cval;
static inline u64 arch_counter_get_cntvct(void)
{
u64 cval;
asm volatile("msr cntkctl_el1, %0" : : "r" (cntkctl));
}
asm volatile("msr cntkctl_el1, %0" : : "r" (cntkctl));
}
-static inline u64 arch_counter_get_cntpct(void)
-{
- u64 cval;
-
- isb();
- asm volatile("mrs %0, cntpct_el0" : "=r" (cval));
-
- return cval;
-}
-
static inline u64 arch_counter_get_cntvct(void)
{
u64 cval;
static inline u64 arch_counter_get_cntvct(void)
{
u64 cval;
return arch_timer_rate;
}
return arch_timer_rate;
}
-/*
- * Some external users of arch_timer_read_counter (e.g. sched_clock) may try to
- * call it before it has been initialised. Rather than incur a performance
- * penalty checking for initialisation, provide a default implementation that
- * won't lead to time appearing to jump backwards.
- */
-static u64 arch_timer_read_zero(void)
+u64 arch_timer_read_counter(void)
+ return arch_counter_get_cntvct();
-u64 (*arch_timer_read_counter)(void) = arch_timer_read_zero;
-
static cycle_t arch_counter_read(struct clocksource *cs)
{
static cycle_t arch_counter_read(struct clocksource *cs)
{
- return arch_timer_read_counter();
+ return arch_counter_get_cntvct();
}
static cycle_t arch_counter_read_cc(const struct cyclecounter *cc)
{
}
static cycle_t arch_counter_read_cc(const struct cyclecounter *cc)
{
- return arch_timer_read_counter();
+ return arch_counter_get_cntvct();
}
static struct clocksource clocksource_counter = {
}
static struct clocksource clocksource_counter = {
cyclecounter.mult = clocksource_counter.mult;
cyclecounter.shift = clocksource_counter.shift;
timecounter_init(&timecounter, &cyclecounter,
cyclecounter.mult = clocksource_counter.mult;
cyclecounter.shift = clocksource_counter.shift;
timecounter_init(&timecounter, &cyclecounter,
- arch_counter_get_cntpct());
+ arch_counter_get_cntvct());
if (arch_timer_use_virtual) {
ppi = arch_timer_ppi[VIRT_PPI];
if (arch_timer_use_virtual) {
ppi = arch_timer_ppi[VIRT_PPI];
- if (arch_timer_use_virtual)
- arch_timer_read_counter = arch_counter_get_cntvct;
- else
- arch_timer_read_counter = arch_counter_get_cntpct;
-
arch_timer_register();
arch_timer_arch_init();
}
arch_timer_register();
arch_timer_arch_init();
}
#ifdef CONFIG_ARM_ARCH_TIMER
extern u32 arch_timer_get_rate(void);
#ifdef CONFIG_ARM_ARCH_TIMER
extern u32 arch_timer_get_rate(void);
-extern u64 (*arch_timer_read_counter)(void);
+extern u64 arch_timer_read_counter(void);
extern struct timecounter *arch_timer_get_timecounter(void);
#else
extern struct timecounter *arch_timer_get_timecounter(void);
#else