clocksource: arch_timer: use virtual counters
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>
This commit is contained in:
Родитель
f793c23ebb
Коммит
0d651e4e65
|
@ -80,15 +80,6 @@ static inline u32 arch_timer_get_cntfrq(void)
|
|||
return val;
|
||||
}
|
||||
|
||||
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;
|
||||
|
|
|
@ -110,16 +110,6 @@ static inline void __cpuinit arch_counter_set_user_access(void)
|
|||
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;
|
||||
|
|
|
@ -186,27 +186,19 @@ u32 arch_timer_get_rate(void)
|
|||
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 0;
|
||||
return arch_counter_get_cntvct();
|
||||
}
|
||||
|
||||
u64 (*arch_timer_read_counter)(void) = arch_timer_read_zero;
|
||||
|
||||
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)
|
||||
{
|
||||
return arch_timer_read_counter();
|
||||
return arch_counter_get_cntvct();
|
||||
}
|
||||
|
||||
static struct clocksource clocksource_counter = {
|
||||
|
@ -287,7 +279,7 @@ static int __init arch_timer_register(void)
|
|||
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];
|
||||
|
@ -376,11 +368,6 @@ static void __init arch_timer_init(struct device_node *np)
|
|||
}
|
||||
}
|
||||
|
||||
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();
|
||||
}
|
||||
|
|
|
@ -32,7 +32,7 @@
|
|||
#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
|
||||
|
|
Загрузка…
Ссылка в новой задаче