On 04/20/2010 06:54 PM, Marcelo Tosatti wrote:
The assigned device interrupt work handler calls kvm_set_irq, which can sleep, for example, waiting for the ioapic mutex, from irq disabled section. https://bugzilla.kernel.org/show_bug.cgi?id=15725 Fix by dropping assigned_dev_lock (and re-enabling interrupts) before invoking kvm_set_irq for the KVM_DEV_IRQ_HOST_MSIX case. Other cases do not require the lock or interrupts disabled (a new work instance will be queued in case of concurrent interrupt). KVM-Stable-Tag. Signed-off-by: Marcelo Tosatti<mtosatti@xxxxxxxxxx> diff --git a/virt/kvm/assigned-dev.c b/virt/kvm/assigned-dev.c index 47ca447..7ac7bbe 100644 --- a/virt/kvm/assigned-dev.c +++ b/virt/kvm/assigned-dev.c @@ -64,24 +64,33 @@ static void kvm_assigned_dev_interrupt_work_handler(struct work_struct *work) interrupt_work); kvm = assigned_dev->kvm; - 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 = assigned_dev->guest_msix_entries; + + spin_lock_irq(&assigned_dev->assigned_dev_lock); for (i = 0; i< assigned_dev->entries_nr; i++) { if (!(guest_entries[i].flags& KVM_ASSIGNED_MSIX_PENDING)) continue; guest_entries[i].flags&= ~KVM_ASSIGNED_MSIX_PENDING; + /* + * If kvm_assigned_dev_intr sets pending for an + * entry smaller than this work instance is + * currently processing, a new work instance + * will be queued. + */ + spin_unlock_irq(&assigned_dev->assigned_dev_lock);
What happens if assigned_dev->entries_nr is changed here?
kvm_set_irq(assigned_dev->kvm, assigned_dev->irq_source_id, guest_entries[i].vector, 1); + spin_lock_irq(&assigned_dev->assigned_dev_lock); } + spin_unlock_irq(&assigned_dev->assigned_dev_lock); } else kvm_set_irq(assigned_dev->kvm, assigned_dev->irq_source_id, assigned_dev->guest_irq, 1); - spin_unlock_irq(&assigned_dev->assigned_dev_lock); }
A less dangerous fix is to copy all vectors to be triggered into a local array, drop the lock, and replay the array into kvm_set_irq(). The else branch could do this as well.
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