KVM: ioapic: fix lost interrupt when changing a device's irq

The ioapic acknowledge path translates interrupt vectors to irqs.  It
currently uses a first match algorithm, stopping when it finds the first
redirection table entry containing the vector.  That fails however if the
guest changes the irq to a different line, leaving the old redirection table
entry in place (though masked).  Result is interrupts not making it to the
guest.

Fix by always scanning the entire redirection table.

Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 11 insertions, 20 deletions

diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
index 98778cb69c6e..1dcf9f3d1107 100644
--- a/virt/kvm/ioapic.c
+++ b/virt/kvm/ioapic.c
@@ -269,28 +269,9 @@ void kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level)
         }
 }
 
-static int get_eoi_gsi(struct kvm_ioapic *ioapic, int vector)
+static void __kvm_ioapic_update_eoi(struct kvm_ioapic *ioapic, int gsi)
 {
-        int i;
-
-        for (i = 0; i < IOAPIC_NUM_PINS; i++)
-                if (ioapic->redirtbl[i].fields.vector == vector)
-                        return i;
-        return -1;
-}
-
-void kvm_ioapic_update_eoi(struct kvm *kvm, int vector)
-{
-        struct kvm_ioapic *ioapic = kvm->arch.vioapic;
         union ioapic_redir_entry *ent;
-        int gsi;
-
-        gsi = get_eoi_gsi(ioapic, vector);
-        if (gsi == -1) {
-                printk(KERN_WARNING "Can't find redir item for %d EOI\n",
-                       vector);
-                return;
-        }
 
         ent = &ioapic->redirtbl[gsi];
         ASSERT(ent->fields.trig_mode == IOAPIC_LEVEL_TRIG);
@@ -300,6 +281,16 @@ void kvm_ioapic_update_eoi(struct kvm *kvm, int vector)
                 ioapic_deliver(ioapic, gsi);
 }
 
+void kvm_ioapic_update_eoi(struct kvm *kvm, int vector)
+{
+        struct kvm_ioapic *ioapic = kvm->arch.vioapic;
+        int i;
+
+        for (i = 0; i < IOAPIC_NUM_PINS; i++)
+                if (ioapic->redirtbl[i].fields.vector == vector)
+                        __kvm_ioapic_update_eoi(ioapic, i);
+}
+
 static int ioapic_in_range(struct kvm_io_device *this, gpa_t addr)
 {
         struct kvm_ioapic *ioapic = (struct kvm_ioapic *)this->private;