[xen staging] x86/hvm: don't force vCPU 0 for IRQ 0 when using fixed destination mode

[patchbot@xxxxxxx]

commit ab5bfc049e8e04bca66d591ab439d2341623f83c
Author:     Roger Pau Monne <roger.pau@xxxxxxxxxx>
AuthorDate: Mon Jul 27 19:05:36 2020 +0200
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Tue Jul 28 19:33:28 2020 +0100

    x86/hvm: don't force vCPU 0 for IRQ 0 when using fixed destination mode
    
    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>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 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 b00037ea87..123191db75 100644
--- a/xen/arch/x86/hvm/vioapic.c
+++ b/xen/arch/x86/hvm/vioapic.c
@@ -438,26 +438,11 @@ 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)) && pt_active(&d->arch.vpit.pt0) )
-        {
-            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:
     {
--
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