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 IO-APIC or MSI
originating vectors as having a pending request when the vLAPIC is in
this state. Such interrupts are simply lost.

Introduce (IO-APIC) or re-use (MSI) a local variable to help
readability.

Fixes: 4fe21ad3712e ("This patch add virtual IOAPIC support for VMX guest")
Fixes: 85715f4bc7c9 ("MSI 5/6: add MSI support to passthrough HVM domain")
Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/arch/x86/hvm/vioapic.c
+++ b/xen/arch/x86/hvm/vioapic.c
@@ -460,9 +460,14 @@ static void vioapic_deliver(struct hvm_v
 
     case dest_Fixed:
         for_each_vcpu ( d, v )
-            if ( vlapic_match_dest(vcpu_vlapic(v), NULL, 0, dest, dest_mode) )
-                ioapic_inj_irq(vioapic, vcpu_vlapic(v), vector, trig_mode,
+        {
+            struct vlapic *vlapic = vcpu_vlapic(v);
+
+            if ( vlapic_enabled(vlapic) &&
+                 vlapic_match_dest(vlapic, NULL, 0, dest, dest_mode) )
+                ioapic_inj_irq(vioapic, vlapic, vector, trig_mode,
                                delivery_mode);
+        }
         break;
 
     case dest_NMI:
--- a/xen/arch/x86/hvm/vmsi.c
+++ b/xen/arch/x86/hvm/vmsi.c
@@ -87,10 +87,12 @@ int vmsi_deliver(
 
     case dest_Fixed:
         for_each_vcpu ( d, v )
-            if ( vlapic_match_dest(vcpu_vlapic(v), NULL,
-                                   0, dest, dest_mode) )
-                vmsi_inj_irq(vcpu_vlapic(v), vector,
-                             trig_mode, delivery_mode);
+        {
+            target = vcpu_vlapic(v);
+            if ( vlapic_enabled(target) &&
+                 vlapic_match_dest(target, NULL, 0, dest, dest_mode) )
+                vmsi_inj_irq(target, vector, trig_mode, delivery_mode);
+        }
         break;
 
     default:

On 21/11/2022 12:13, Jan Beulich wrote:
> 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 IO-APIC or MSI
> originating vectors as having a pending request when the vLAPIC is in
> this state. Such interrupts are simply lost.
>
> Introduce (IO-APIC) or re-use (MSI) a local variable to help
> readability.
>
> Fixes: 4fe21ad3712e ("This patch add virtual IOAPIC support for VMX guest")
> Fixes: 85715f4bc7c9 ("MSI 5/6: add MSI support to passthrough HVM domain")
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>