[PATCH] x86/Viridian: don't mark IRQ vectors as pending when vLAPIC is disabled

[Jan Beulich]

In software-disabled state an LAPIC does not accept any interrupt
requests and hence no IRR bit would newly become set while in this
state. As a result it is also wrong for us to mark Viridian IPI or timer
vectors as having a pending request when the vLAPIC is in this state.
Such interrupts are simply lost.

Introduce a local variable in send_ipi() to help readability.

Fixes: fda96b7382ea ("viridian: add implementation of the 
HvSendSyntheticClusterIpi hypercall")
Fixes: 26fba3c85571 ("viridian: add implementation of synthetic timers")
Signed-off-by: Jan Beulich <jbeul...@suse.com>

--- a/xen/arch/x86/hvm/viridian/synic.c
+++ b/xen/arch/x86/hvm/viridian/synic.c
@@ -359,7 +359,7 @@ bool viridian_synic_deliver_timer_msg(st
     BUILD_BUG_ON(sizeof(payload) > sizeof(msg->u.payload));
     memcpy(msg->u.payload, &payload, sizeof(payload));
 
-    if ( !vs->masked )
+    if ( !vs->masked && vlapic_enabled(vcpu_vlapic(v)) )
         vlapic_set_irq(vcpu_vlapic(v), vs->vector, 0);
 
     return true;
--- a/xen/arch/x86/hvm/viridian/viridian.c
+++ b/xen/arch/x86/hvm/viridian/viridian.c
@@ -811,7 +811,12 @@ static void send_ipi(struct hypercall_vp
         cpu_raise_softirq_batch_begin();
 
     for_each_vp ( vpmask, vp )
-        vlapic_set_irq(vcpu_vlapic(currd->vcpu[vp]), vector, 0);
+    {
+        struct vlapic *vlapic = vcpu_vlapic(currd->vcpu[vp]);
+
+        if ( vlapic_enabled(vlapic) )
+            vlapic_set_irq(vlapic, vector, 0);
+    }
 
     if ( nr > 1 )
         cpu_raise_softirq_batch_finish();