[PATCH 1/4] Move irq routing data structure to rcu locking

Gleb Natapov
2009-07-12T12:03:56Z

Signed-off-by: Gleb Natapov <gleb@redhat.com>
---
include/linux/kvm_host.h | 2 +-
virt/kvm/irq_comm.c | 55 +++++++++++++++++++++-------------------------
virt/kvm/kvm_main.c | 1 -
3 files changed, 26 insertions(+), 32 deletions(-)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index f54a0d3..6756b3e 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -161,7 +161,7 @@ struct kvm {

struct mutex irq_lock;
#ifdef CONFIG_HAVE_KVM_IRQCHIP
- struct list_head irq_routing; /* of kvm_kernel_irq_routing_entry */
+ struct kvm_kernel_irq_routing_entry *irq_routing;
struct hlist_head mask_notifier_list;
#endif

diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
index 7af18b8..b2fa3f6 100644
--- a/virt/kvm/irq_comm.c
+++ b/virt/kvm/irq_comm.c
@@ -148,7 +148,8 @@ int kvm_set_irq(struct kvm *kvm, int irq_source_id, int irq, int level)
* IOAPIC. So set the bit in both. The guest will ignore
* writes to the unused one.
*/
- list_for_each_entry(e, &kvm->irq_routing, link)
+ rcu_read_lock();
+ for (e = rcu_dereference(kvm->irq_routing); e && e->set; e++) {
if (e->gsi == irq) {
int r = e->set(e, kvm, sig_level);
if (r < 0)
@@ -156,6 +157,8 @@ int kvm_set_irq(struct kvm *kvm, int irq_source_id, int irq, int level)

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

@@ -168,12 +171,15 @@ void kvm_notify_acked_irq(struct kvm *kvm, unsigned irqchip, unsigned pin)

trace_kvm_ack_irq(irqchip, pin);

- list_for_each_entry(e, &kvm->irq_routing, link)
+ rcu_read_lock();
+ for (e = rcu_dereference(kvm->irq_routing); e && e->set; e++) {
if (e->irqchip.irqchip == irqchip &&
e->irqchip.pin == pin) {
gsi = e->gsi;
break;
}
+ }
+ rcu_read_unlock();

hlist_for_each_entry(kian, n, &kvm->arch.irq_ack_notifier_list, link)
if (kian->gsi == gsi)
@@ -264,19 +270,11 @@ void kvm_fire_mask_notifiers(struct kvm *kvm, int irq, bool mask)
kimn->func(kimn, mask);
}

-static void __kvm_free_irq_routing(struct list_head *irq_routing)
-{
- struct kvm_kernel_irq_routing_entry *e, *n;
-
- list_for_each_entry_safe(e, n, irq_routing, link)
- kfree(e);
-}
-
void kvm_free_irq_routing(struct kvm *kvm)
{
- mutex_lock(&kvm->irq_lock);
- __kvm_free_irq_routing(&kvm->irq_routing);
- mutex_unlock(&kvm->irq_lock);
+ /* Called only during vm destruction. Nobody can use the pointer
+ at this stage */
+ kfree(kvm->irq_routing);
}

static int setup_routing_entry(struct kvm_kernel_irq_routing_entry *e,
@@ -326,43 +324,40 @@ int kvm_set_irq_routing(struct kvm *kvm,
unsigned nr,
unsigned flags)
{
- struct list_head irq_list = LIST_HEAD_INIT(irq_list);
- struct list_head tmp = LIST_HEAD_INIT(tmp);
- struct kvm_kernel_irq_routing_entry *e = NULL;
+ struct kvm_kernel_irq_routing_entry *new, *old;
unsigned i;
int r;

+ /* last element is left zeroed and indicates the end of the array */
+ new = kzalloc(sizeof(*new) * (nr + 1), GFP_KERNEL);
+
+ if (!new)
+ return -ENOMEM;
+
for (i = 0; i < nr; ++i) {
r = -EINVAL;
if (ue->gsi >= KVM_MAX_IRQ_ROUTES)
goto out;
if (ue->flags)
goto out;
- r = -ENOMEM;
- e = kzalloc(sizeof(*e), GFP_KERNEL);
- if (!e)
- goto out;
- r = setup_routing_entry(e, ue);
+ r = setup_routing_entry(new + i, ue);
if (r)
goto out;
++ue;
- list_add(&e->link, &irq_list);
- e = NULL;
}

mutex_lock(&kvm->irq_lock);
- list_splice(&kvm->irq_routing, &tmp);
- INIT_LIST_HEAD(&kvm->irq_routing);
- list_splice(&irq_list, &kvm->irq_routing);
- INIT_LIST_HEAD(&irq_list);
- list_splice(&tmp, &irq_list);
+ old = kvm->irq_routing;
+ rcu_assign_pointer(kvm->irq_routing, new);
mutex_unlock(&kvm->irq_lock);

+ synchronize_rcu();
+
r = 0;
+ new = old;

out:
- kfree(e);
- __kvm_free_irq_routing(&irq_list);
+ kfree(new);
return r;
}

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index cf20dc1..24013b4 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -945,7 +945,6 @@ static struct kvm *kvm_create_vm(void)
if (IS_ERR(kvm))
goto out;
#ifdef CONFIG_HAVE_KVM_IRQCHIP
- INIT_LIST_HEAD(&kvm->irq_routing);
INIT_HLIST_HEAD(&kvm->mask_notifier_list);
#endif

--
1.6.2.1