When the divide value change, uptade the timer according to the new
value, and keep the Counter Register (TMCCT) value the same between
before and after the divisor change.
Signed-off-by: Anthony PERARD <anthony.per...@citrix.com>
---
xen/arch/x86/hvm/vlapic.c | 30 ++++++++++++++++++++++++++++++
1 file changed, 30 insertions(+)
diff --git a/xen/arch/x86/hvm/vlapic.c b/xen/arch/x86/hvm/vlapic.c
index 97b7774b61..f70a25f5b9 100644
--- a/xen/arch/x86/hvm/vlapic.c
+++ b/xen/arch/x86/hvm/vlapic.c
@@ -705,6 +705,35 @@ static void vlapic_update_timer(struct vlapic *vlapic,
is_periodic = vlapic_lvtt_period(vlapic);
is_oneshot = vlapic_lvtt_oneshot(vlapic);
break;
+ case APIC_TDCR:
+ is_periodic = vlapic_lvtt_period(vlapic);
+ is_oneshot = vlapic_lvtt_oneshot(vlapic);
+
+ period = (uint64_t)vlapic_get_reg(vlapic, APIC_TMICT)
+ * APIC_BUS_CYCLE_NS * vlapic->hw.timer_divisor;
+
+ /* Calculate the next time the timer should trigger an interrupt. */
+ if ( period && vlapic->timer_last_update )
+ {
+ uint64_t time_passed = hvm_get_guest_time(current)
+ - vlapic->timer_last_update;
+ if ( is_periodic )
+ time_passed %= period;
+ if ( time_passed < period )
+ delta = period - time_passed;
+ }
+
+ val = ((val & 3) | ((val & 8) >> 1)) + 1;
+ val = 1 << (val & 7);
+
+ period = (uint64_t)vlapic_get_reg(vlapic, APIC_TMICT)
+ * APIC_BUS_CYCLE_NS * val;
+
+ /* Calculate time left until next interrupt, base on the difference
+ * between the current timer_divisor and the new one */
+ delta = delta * val / vlapic->hw.timer_divisor;
+
+ break;
default:
BUG();
}
@@ -848,6 +877,7 @@ static void vlapic_reg_write(struct vcpu *v,
break;
case APIC_TDCR:
+ vlapic_update_timer(vlapic, APIC_TDCR, val);
vlapic_set_tdcr(vlapic, val & 0xb);
HVM_DBG_LOG(DBG_LEVEL_VLAPIC_TIMER, "timer divisor is %#x",
vlapic->hw.timer_divisor);
--
Anthony PERARD
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