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KVM: Avoid redelivery of edge interrupt before next edge
The check for an edge is broken in current ioapic code. ioapic->irr is cleared on each edge interrupt by ioapic_service() and this makes old_irr != ioapic->irr condition in kvm_ioapic_set_irq() to be always true. The patch fixes the code to properly recognise edge. Some HW emulation calls set_irq() without level change. If each such call is propagated to an OS it may confuse a device driver. This is the case with keyboard device emulation and Windows XP x64 installer on SMP VM. Each keystroke produce two interrupts (down/up) one interrupt is submitted to CPU0 and another to CPU1. This confuses Windows somehow and it ignores keystrokes. Signed-off-by: Gleb Natapov <firstname.lastname@example.org> Signed-off-by: Avi Kivity <email@example.com>
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