ff4b9df877
There's a bug in the IOAPIC code for level-triggered interrupts. Its relatively easy to trigger by sharing (virtio-blk + usbtablet was the testcase, initially reported by Gerd von Egidy). The "remote_irr" variable is used to indicate accepted but not yet acked interrupts. Its cleared from the EOI handler. Problem is that the EOI handler clears remote_irr unconditionally, even if it reinjected another pending interrupt. In that case, kvm_ioapic_set_irq() proceeds to ioapic_service() which sets remote_irr even if it failed to inject (since the IRR was high due to EOI reinjection). Since the TMR bit has been cleared by the first EOI, the second one fails to clear remote_irr. End result is interrupt line dead. Fix it by setting remote_irr only if a new pending interrupt has been generated (and the TMR bit for vector in question set). Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Avi Kivity <avi@qumranet.com> |
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