[PATCH for-4.14 2/8] x86/hvm: don't force vCPU 0 for IRQ 0 when using fixed destination mode

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

When the IO APIC pin mapped to the ISA IRQ 0 has been configured to
use fixed delivery mode do not forcefully route interrupts to vCPU 0,
as the OS might have setup those interrupts to be injected to a
different vCPU, and injecting to vCPU 0 can cause the OS to miss such
interrupts or errors to happen due to unexpected vectors being
injected on vCPU 0.

In order to fix remove such handling altogether for fixed destination
mode pins and just inject them according to the data setup in the
IO-APIC entry.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 xen/arch/x86/hvm/vioapic.c | 23 ++++-------------------
 1 file changed, 4 insertions(+), 19 deletions(-)

diff --git a/xen/arch/x86/hvm/vioapic.c b/xen/arch/x86/hvm/vioapic.c
index bd41036137..67472e5934 100644
--- a/xen/arch/x86/hvm/vioapic.c
+++ b/xen/arch/x86/hvm/vioapic.c
@@ -445,26 +445,11 @@ static void vioapic_deliver(struct hvm_vioapic *vioapic, 
unsigned int pin)
     }
 
     case dest_Fixed:
-    {
-#ifdef IRQ0_SPECIAL_ROUTING
-        /* Do not deliver timer interrupts to VCPU != 0 */
-        if ( (irq == hvm_isa_irq_to_gsi(0)) && pit_channel0_enabled() )
-        {
-            if ( (v = d->vcpu ? d->vcpu[0] : NULL) != NULL )
-                ioapic_inj_irq(vioapic, vcpu_vlapic(v), vector,
-                               trig_mode, delivery_mode);
-        }
-        else
-#endif
-        {
-            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, delivery_mode);
-        }
+        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,
+                               delivery_mode);
         break;
-    }
 
     case dest_NMI:
     {
-- 
2.26.2