[PATCH 12/42] KVM: Move irq routing data structure to rcu locking

Avi Kivity
2009-11-16T12:29:13Z

From: Gleb Natapov <gleb@redhat.com>

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
---
virt/kvm/irq_comm.c | 16 +++++++++++-----
1 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
index 59cf8da..fb861dd 100644
--- a/virt/kvm/irq_comm.c
+++ b/virt/kvm/irq_comm.c
@@ -159,7 +159,8 @@ int kvm_set_irq(struct kvm *kvm, int irq_source_id, u32 irq, int level)
* IOAPIC. So set the bit in both. The guest will ignore
* writes to the unused one.
*/
- irq_rt = kvm->irq_routing;
+ rcu_read_lock();
+ irq_rt = rcu_dereference(kvm->irq_routing);
if (irq < irq_rt->nr_rt_entries)
hlist_for_each_entry(e, n, &irq_rt->map[irq], link) {
int r = e->set(e, kvm, irq_source_id, level);
@@ -168,6 +169,7 @@ int kvm_set_irq(struct kvm *kvm, int irq_source_id, u32 irq, int level)

ret = r + ((ret < 0) ? 0 : ret);
}
+ rcu_read_unlock();
return ret;
}

@@ -179,7 +181,10 @@ void kvm_notify_acked_irq(struct kvm *kvm, unsigned irqchip, unsigned pin)

trace_kvm_ack_irq(irqchip, pin);

- gsi = kvm->irq_routing->chip[irqchip][pin];
+ rcu_read_lock();
+ gsi = rcu_dereference(kvm->irq_routing)->chip[irqchip][pin];
+ rcu_read_unlock();
+
if (gsi != -1)
hlist_for_each_entry(kian, n, &kvm->arch.irq_ack_notifier_list,
link)
@@ -279,9 +284,9 @@ void kvm_fire_mask_notifiers(struct kvm *kvm, int irq, bool mask)

void kvm_free_irq_routing(struct kvm *kvm)
{
- mutex_lock(&kvm->irq_lock);
+ /* Called only during vm destruction. Nobody can use the pointer
+ at this stage */
kfree(kvm->irq_routing);
- mutex_unlock(&kvm->irq_lock);
}

static int setup_routing_entry(struct kvm_irq_routing_table *rt,
@@ -387,8 +392,9 @@ int kvm_set_irq_routing(struct kvm *kvm,

mutex_lock(&kvm->irq_lock);
old = kvm->irq_routing;
- kvm->irq_routing = new;
+ rcu_assign_pointer(kvm->irq_routing, new);
mutex_unlock(&kvm->irq_lock);
+ synchronize_rcu();

new = old;
r = 0;
--
1.6.5.2