x86/HVM: assorted RTC emulation adjustments

- only call check_update_timer() on REG_B writes when SET changes
- only call alarm_timer_update() on REG_B writes when relevant bits
  change
- instead properly handle AF and PF when the guest is not also setting
  AIE/PIE respectively (for UF this was already the case, only a
  comment was slightly inaccurate), including calling the respective
  update functions upon REG_C reads

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Tested-by: Olaf Hering <olaf@aepfle.de>

1 files changed, 5 insertions, 2 deletions

diff --git a/xen/arch/x86/hvm/vpt.c b/xen/arch/x86/hvm/vpt.c
index 15abad8b82..46d3ec6c97 100644
--- a/xen/arch/x86/hvm/vpt.c
+++ b/xen/arch/x86/hvm/vpt.c
@@ -22,6 +22,7 @@
 #include <asm/hvm/vpt.h>
 #include <asm/event.h>
 #include <asm/apic.h>
+#include <asm/mc146818rtc.h>
 
 #define mode_is(d, name) \
     ((d)->arch.hvm_domain.params[HVM_PARAM_TIMER_MODE] == HVMPTM_##name)
@@ -218,6 +219,7 @@ int pt_update_irq(struct vcpu *v)
     struct periodic_time *pt, *temp, *earliest_pt = NULL;
     uint64_t max_lag = -1ULL;
     int irq, is_lapic;
+    void *pt_priv;
 
     spin_lock(&v->arch.hvm_vcpu.tm_lock);
 
@@ -251,13 +253,14 @@ int pt_update_irq(struct vcpu *v)
     earliest_pt->irq_issued = 1;
     irq = earliest_pt->irq;
     is_lapic = (earliest_pt->source == PTSRC_lapic);
+    pt_priv = earliest_pt->priv;
 
     spin_unlock(&v->arch.hvm_vcpu.tm_lock);
 
     if ( is_lapic )
-    {
         vlapic_set_irq(vcpu_vlapic(v), irq, 0);
-    }
+    else if ( irq == RTC_IRQ && pt_priv )
+        rtc_periodic_interrupt(pt_priv);
     else
     {
         hvm_isa_irq_deassert(v->domain, irq);