[PATCH 02/10] Move irq routing data structure to rcu locking

[Gleb Natapov]

Signed-off-by: Gleb Natapov <g...@redhat.com>
---
 virt/kvm/irq_comm.c |   15 ++++++++++-----
 1 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
index 2ab807f..9cdd984 100644
--- a/virt/kvm/irq_comm.c
+++ b/virt/kvm/irq_comm.c
@@ -152,7 +152,8 @@ 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.
         */
-       irq_rt = kvm->irq_routing;
+       rcu_read_lock();
+       irq_rt = rcu_dereference(kvm->irq_routing);
        if (irq < irq_rt->max_gsi)
                hlist_for_each_entry(e, n, &irq_rt->map[irq], link) {
                        int r = e->set(e, kvm, sig_level);
@@ -161,6 +162,7 @@ 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;
 }
 
@@ -172,9 +174,11 @@ 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];
        if (gsi == -1)
                gsi = pin;
+       rcu_read_unlock();
 
        hlist_for_each_entry(kian, n, &kvm->arch.irq_ack_notifier_list, link)
                if (kian->gsi == gsi)
@@ -267,9 +271,9 @@ 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,
@@ -364,8 +368,9 @@ 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;
-- 
1.6.3.3

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