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author | 2009-01-06 10:03:03 +0800 | |
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committer | 2009-02-15 02:47:36 +0200 | |
commit | ba4cef31d5a397b64ba6d3ff713ce06c62f0c597 (patch) | |
tree | 50a0c4cbcad5d543dd9572c5911cc288b88c3c56 /virt/kvm/kvm_main.c | |
parent | KVM: Add kvm_arch_sync_events to sync with asynchronize events (diff) | |
download | linux-ba4cef31d5a397b64ba6d3ff713ce06c62f0c597.tar.gz linux-ba4cef31d5a397b64ba6d3ff713ce06c62f0c597.tar.bz2 linux-ba4cef31d5a397b64ba6d3ff713ce06c62f0c597.zip |
KVM: Fix racy in kvm_free_assigned_irq
In the past, kvm_get_kvm() and kvm_put_kvm() was called in assigned device irq
handler and interrupt_work, in order to prevent cancel_work_sync() in
kvm_free_assigned_irq got a illegal state when waiting for interrupt_work done.
But it's tricky and still got two problems:
1. A bug ignored two conditions that cancel_work_sync() would return true result
in a additional kvm_put_kvm().
2. If interrupt type is MSI, we would got a window between cancel_work_sync()
and free_irq(), which interrupt would be injected again...
This patch discard the reference count used for irq handler and interrupt_work,
and ensure the legal state by moving the free function at the very beginning of
kvm_destroy_vm(). And the patch fix the second bug by disable irq before
cancel_work_sync(), which may result in nested disable of irq but OK for we are
going to free it.
Signed-off-by: Sheng Yang <sheng@linux.intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Diffstat (limited to 'virt/kvm/kvm_main.c')
-rw-r--r-- | virt/kvm/kvm_main.c | 27 |
1 files changed, 19 insertions, 8 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 68e3f1ec1674..277ea7f39fc8 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -173,7 +173,6 @@ static void kvm_assigned_dev_interrupt_work_handler(struct work_struct *work) assigned_dev->host_irq_disabled = false; } mutex_unlock(&assigned_dev->kvm->lock); - kvm_put_kvm(assigned_dev->kvm); } static irqreturn_t kvm_assigned_dev_intr(int irq, void *dev_id) @@ -181,8 +180,6 @@ static irqreturn_t kvm_assigned_dev_intr(int irq, void *dev_id) struct kvm_assigned_dev_kernel *assigned_dev = (struct kvm_assigned_dev_kernel *) dev_id; - kvm_get_kvm(assigned_dev->kvm); - schedule_work(&assigned_dev->interrupt_work); disable_irq_nosync(irq); @@ -213,6 +210,7 @@ static void kvm_assigned_dev_ack_irq(struct kvm_irq_ack_notifier *kian) } } +/* The function implicit hold kvm->lock mutex due to cancel_work_sync() */ static void kvm_free_assigned_irq(struct kvm *kvm, struct kvm_assigned_dev_kernel *assigned_dev) { @@ -228,11 +226,24 @@ static void kvm_free_assigned_irq(struct kvm *kvm, if (!assigned_dev->irq_requested_type) return; - if (cancel_work_sync(&assigned_dev->interrupt_work)) - /* We had pending work. That means we will have to take - * care of kvm_put_kvm. - */ - kvm_put_kvm(kvm); + /* + * In kvm_free_device_irq, cancel_work_sync return true if: + * 1. work is scheduled, and then cancelled. + * 2. work callback is executed. + * + * The first one ensured that the irq is disabled and no more events + * would happen. But for the second one, the irq may be enabled (e.g. + * for MSI). So we disable irq here to prevent further events. + * + * Notice this maybe result in nested disable if the interrupt type is + * INTx, but it's OK for we are going to free it. + * + * If this function is a part of VM destroy, please ensure that till + * now, the kvm state is still legal for probably we also have to wait + * interrupt_work done. + */ + disable_irq_nosync(assigned_dev->host_irq); + cancel_work_sync(&assigned_dev->interrupt_work); free_irq(assigned_dev->host_irq, (void *)assigned_dev); |