From 51026309522dc0a08cf25c64db828ef078c66596 Mon Sep 17 00:00:00 2001 From: "kaf24@firebug.cl.cam.ac.uk" Date: Mon, 25 Jul 2005 21:03:40 +0000 Subject: [PATCH] Improve guest time keeping Even though we accounted for lost ticks, the accounting was not precise. Specifically, we didn't account for the delay in calling the ac_timer handler. Signed-off-by: Eddie Dong Signed-off-by: Arun Sharma --- xen/arch/x86/vmx_intercept.c | 16 ++++++++++++++-- xen/include/asm-x86/vmx_virpit.h | 1 + 2 files changed, 15 insertions(+), 2 deletions(-) diff --git a/xen/arch/x86/vmx_intercept.c b/xen/arch/x86/vmx_intercept.c index 15b8caf371..4252d923fa 100644 --- a/xen/arch/x86/vmx_intercept.c +++ b/xen/arch/x86/vmx_intercept.c @@ -197,12 +197,23 @@ int intercept_pit_io(ioreq_t *p) static void pit_timer_fn(void *data) { struct vmx_virpit_t *vpit = data; + s_time_t next; + int missed_ticks; + + missed_ticks = (NOW() - vpit->scheduled) / MILLISECS(vpit->period); /* Set the pending intr bit, and send evtchn notification to myself. */ if (test_and_set_bit(vpit->vector, vpit->intr_bitmap)) vpit->pending_intr_nr++; /* already set, then count the pending intr */ - set_ac_timer(&vpit->pit_timer, NOW() + MILLISECS(vpit->period)); + /* pick up missed timer tick */ + if ( missed_ticks > 0 ) { + vpit->pending_intr_nr+= missed_ticks; + vpit->scheduled += missed_ticks * MILLISECS(vpit->period); + } + next = vpit->scheduled + MILLISECS(vpit->period); + set_ac_timer(&vpit->pit_timer, next); + vpit->scheduled = next; } @@ -263,7 +274,8 @@ void vmx_hooks_assist(struct vcpu *d) vpit->intr_bitmap = intr; - set_ac_timer(&vpit->pit_timer, NOW() + MILLISECS(vpit->period)); + vpit->scheduled = NOW() + MILLISECS(vpit->period); + set_ac_timer(&vpit->pit_timer, vpit->scheduled); /*restore the state*/ p->state = STATE_IORESP_READY; diff --git a/xen/include/asm-x86/vmx_virpit.h b/xen/include/asm-x86/vmx_virpit.h index 6a0a4edab7..64bf9e19f0 100644 --- a/xen/include/asm-x86/vmx_virpit.h +++ b/xen/include/asm-x86/vmx_virpit.h @@ -19,6 +19,7 @@ struct vmx_virpit_t { /* for simulation of counter 0 in mode 2*/ int vector; /* the pit irq vector */ unsigned int period; /* the frequency. e.g. 10ms*/ + s_time_t scheduled; /* scheduled timer interrupt */ unsigned int channel; /* the pit channel, counter 0~2 */ u64 *intr_bitmap; unsigned int pending_intr_nr; /* the couner for pending timer interrupts */ -- 2.30.2