Kernels up to 2.6.31 have a bug: MSI entries where looked at when irq
is acked, address_lo was interpreted as irqchip, and
address_hi as pin. If that matches a real interrupt this prevents
ack notifier from being processed.
Since these kernels ignore the value for address_hi when delivering
MSI, work around this by setting a value that never matches an
interrupt pin number.
Pointers to relevant kernel code, for reference: in kernel v2.6.31-rc3:
kvm_notify_acked_irq - fails to check irq type,
kvm_set_msi - ignored address_hi in message
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
---
qemu-kvm.c | 32 ++++++++++++++++++++++++++++++--
1 files changed, 30 insertions(+), 2 deletions(-)
diff --git a/qemu-kvm.c b/qemu-kvm.c
index cebaa65..ec6d583 100644
--- a/qemu-kvm.c
+++ b/qemu-kvm.c
@@ -38,6 +38,32 @@
#error libkvm: userspace and kernel version mismatch
#endif
+#ifdef KVM_CAP_IRQ_ROUTING
+/* Broken MSI routing work-around:
+ * Kernels up to 2.6.31 have a bug: MSI entries where looked at when irq
+ * is acked, address_lo was interpreted as irqchip, and
+ * address_hi as pin. If that matches a real interrupt this prevents
+ * ack notifier from being processed.
+ *
+ * Since these kernels ignore the value for address_hi when delivering
+ * MSI, work around this by setting a value that never matches an
+ * interrupt pin number.
+ */
+#define KVM_BROKEN_MSI_ROUTING 1
+static inline
+void kvm_broken_msi_fix(struct kvm_irq_routing_entry *entry)
+{
+ if (entry->type == KVM_IRQ_ROUTING_MSI) {
+ entry->u.msi.address_hi = 0xffffffff;
+ }
+}
+static inline
+unsigned kvm_broken_msi_address_hi(struct kvm_irq_routing_entry *entry)
+{
+ return 0xffffffff;
+}
+#endif
+
int kvm_allowed = 1;
int kvm_irqchip = 1;
int kvm_pit = 1;
@@ -1433,6 +1459,7 @@ int kvm_add_routing_entry(kvm_context_t kvm,
new->type = entry->type;
new->flags = entry->flags;
new->u = entry->u;
+ kvm_broken_msi_fix(new);
set_gsi(kvm, entry->gsi);
@@ -1489,7 +1516,7 @@ int kvm_del_routing_entry(kvm_context_t kvm,
if (e->u.msi.address_lo ==
entry->u.msi.address_lo
&& e->u.msi.address_hi ==
- entry->u.msi.address_hi
+ kvm_broken_msi_address_hi(entry)
&& e->u.msi.data == entry->u.msi.data) {
p = &kvm->irq_routes->
entries[--kvm->irq_routes->nr];
@@ -1550,9 +1577,10 @@ int kvm_update_routing_entry(kvm_context_t kvm,
break;
case KVM_IRQ_ROUTING_MSI:
if (e->u.msi.address_lo == entry->u.msi.address_lo &&
- e->u.msi.address_hi == entry->u.msi.address_hi &&
+ e->u.msi.address_hi == kvm_broken_msi_address_hi(entry) &&
e->u.msi.data == entry->u.msi.data) {
memcpy(&e->u.msi, &newentry->u.msi, sizeof e->u.msi);
+ kvm_broken_msi_fix(e);
return 0;
}
break;
--
1.6.2.5
--
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