KVM: Drop kvm->irq_lock lock from irq injection path

The only thing it protects now is interrupt injection into lapic and
this can work lockless. Even now with kvm->irq_lock in place access
to lapic is not entirely serialized since vcpu access doesn't take
kvm->irq_lock.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

3 files changed, 1 insertions, 9 deletions

diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index bb4ebd89b9ff..30f70fd511c4 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -61,10 +61,8 @@ irqfd_inject(struct work_struct *work)
         struct _irqfd *irqfd = container_of(work, struct _irqfd, inject);
         struct kvm *kvm = irqfd->kvm;
 
-        mutex_lock(&kvm->irq_lock);
         kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 1);
         kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 0);
-        mutex_unlock(&kvm->irq_lock);
 }
 
 /*
diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
index fadf4408a820..15a83b93566d 100644
--- a/virt/kvm/irq_comm.c
+++ b/virt/kvm/irq_comm.c
@@ -82,8 +82,6 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,
         int i, r = -1;
         struct kvm_vcpu *vcpu, *lowest = NULL;
 
-        WARN_ON(!mutex_is_locked(&kvm->irq_lock));
-
         if (irq->dest_mode == 0 && irq->dest_id == 0xff &&
                         kvm_is_dm_lowest_prio(irq))
                 printk(KERN_INFO "kvm: apic: phys broadcast and lowest prio\n");
@@ -138,7 +136,7 @@ static int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
         return kvm_irq_delivery_to_apic(kvm, NULL, &irq);
 }
 
-/* This should be called with the kvm->irq_lock mutex held
+/*
  * Return value:
  *  < 0   Interrupt was ignored (masked or not delivered for other reasons)
  *  = 0   Interrupt was coalesced (previous irq is still pending)
@@ -153,8 +151,6 @@ int kvm_set_irq(struct kvm *kvm, int irq_source_id, u32 irq, int level)
 
         trace_kvm_set_irq(irq, level, irq_source_id);
 
-        WARN_ON(!mutex_is_locked(&kvm->irq_lock));
-
         /* Not possible to detect if the guest uses the PIC or the
          * IOAPIC.  So set the bit in both. The guest will ignore
          * writes to the unused one.
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 6eca153e1a02..c12c95b1b641 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -137,7 +137,6 @@ static void kvm_assigned_dev_interrupt_work_handler(struct work_struct *work)
                                     interrupt_work);
         kvm = assigned_dev->kvm;
 
-        mutex_lock(&kvm->irq_lock);
         spin_lock_irq(&assigned_dev->assigned_dev_lock);
         if (assigned_dev->irq_requested_type & KVM_DEV_IRQ_HOST_MSIX) {
                 struct kvm_guest_msix_entry *guest_entries =
@@ -156,7 +155,6 @@ static void kvm_assigned_dev_interrupt_work_handler(struct work_struct *work)
                             assigned_dev->guest_irq, 1);
 
         spin_unlock_irq(&assigned_dev->assigned_dev_lock);
-        mutex_unlock(&assigned_dev->kvm->irq_lock);
 }
 
 static irqreturn_t kvm_assigned_dev_intr(int irq, void *dev_id)