apic: avoid getting out of halted state on masked PIC interrupts

After the next patch, if a masked PIC interrupts causes CPU_INTERRUPT_POLL
to be set, the CPU will spuriously get out of halted state.  While this
is technically valid, we should avoid that.

Make CPU_INTERRUPT_POLL run apic_update_irq in the right thread and then
look at CPU_INTERRUPT_HARD.  If CPU_INTERRUPT_HARD does not get set,
do not report the CPU as having work.

Also move the handling of software-disabled APIC from apic_update_irq
to apic_irq_pending, and always trigger CPU_INTERRUPT_POLL.  This will
be important once we will add a case that resets CPU_INTERRUPT_HARD
from apic_update_irq.  We want to run it even if we go through
CPU_INTERRUPT_POLL, and even if the local APIC is software disabled.
Reported-by: NRichard Bilson <rbilson@qnx.com>
Tested-by: NRichard Bilson <rbilson@qnx.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

hw/intc/apic.c

@@ -349,6 +349,11 @@ static int apic_get_arb_pri(APICCommonState *s)
 static int apic_irq_pending(APICCommonState *s)
 {
     int irrv, ppr;
+
+    if (!(s->spurious_vec & APIC_SV_ENABLE)) {
+        return 0;
+    }
+
     irrv = get_highest_priority_int(s->irr);
     if (irrv < 0) {
         return 0;
@@ -366,9 +371,6 @@ static void apic_update_irq(APICCommonState *s)
 {
     CPUState *cpu;
 
-    if (!(s->spurious_vec & APIC_SV_ENABLE)) {
-        return;
-    }
     cpu = CPU(s->cpu);
     if (!qemu_cpu_is_self(cpu)) {
         cpu_interrupt(cpu, CPU_INTERRUPT_POLL);

target-i386/cpu.c

@@ -2912,8 +2912,14 @@ static bool x86_cpu_has_work(CPUState *cs)
     X86CPU *cpu = X86_CPU(cs);
     CPUX86State *env = &cpu->env;
 
-    return ((cs->interrupt_request & (CPU_INTERRUPT_HARD |
-                                      CPU_INTERRUPT_POLL)) &&
+#if !defined(CONFIG_USER_ONLY)
+    if (cs->interrupt_request & CPU_INTERRUPT_POLL) {
+        apic_poll_irq(cpu->apic_state);
+        cpu_reset_interrupt(cs, CPU_INTERRUPT_POLL);
+    }
+#endif
+
+    return ((cs->interrupt_request & CPU_INTERRUPT_HARD) &&
             (env->eflags & IF_MASK)) ||
            (cs->interrupt_request & (CPU_INTERRUPT_NMI |
                                      CPU_INTERRUPT_INIT |