ARM DDI 0487G.a states on page D13-4180 that, when the virtual timer is enabled, the timer condition is met when CNTVCT_EL0 - CNTV_CVAL_EL0 >= 0. Multiplying both sides of the inequality by -1, we get the equivalent condition CNTV_CVAL_EL0 - CNTVCT_EL0 <= 0 for when the timer should fire.
On the same page, it states that a read of the CNTV_TVAL_EL0 register returns CNTV_CVAL_EL0 - CNTVCT_EL0 if the virtual timer is enabled. Putting the two together, the timer condition is met when the value of the TVAL register is less than or *equal* to 0. Same rules apply for the physical timer. Fix the check for the timer expiring by treating a TVAL value equal to zero as a valid condition for the timer to fire. Signed-off-by: Alexandru Elisei <[email protected]> --- arm/timer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arm/timer.c b/arm/timer.c index 09e3f8f6bd7d..2a6687f22874 100644 --- a/arm/timer.c +++ b/arm/timer.c @@ -277,7 +277,7 @@ static void test_timer(struct timer_info *info) local_irq_enable(); left = info->read_tval(); report(info->irq_received, "interrupt received after TVAL/WFI"); - report(left < 0, "timer has expired"); + report(left <= 0, "timer has expired"); report_info("TVAL is %d ticks", left); } -- 2.34.1 _______________________________________________ kvmarm mailing list [email protected] https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
