On Saturday 07 October 2006 19:15, Donald Liew wrote: > i'm reading qemu-system-arm code and trying to add some more > evaluation boards support for it. in the 0.8.2 source code i found > something i can't understand, when handling interrupts all other > targets clears this bit after calling do_interrupt, however the arm > target doesn't do this, why? won't this cause problems like redundant > interrupts? any special consideration about this?
I this this is the correct behavior. The nIRQ line is level triggered. spurious interrupts are avoided because do_interrupt sets the CPSR_I flag. During normal operation theguest OS will clear the IRQ condition (by masking the interrupt on the PIC or device) before clearing the CPSE_I flag, so it doesn't matter what we do. Consider the case where the guest OS were to clear CPSR_F without touching the IRQ line. In this case we would expect annother IRQ exception to be taken immediately. If (as you suggest above) we cleared CPU_INTERRUPT_HARD in cpu_exec then the IRQ would not be taken until something re-raised the IRQ line. Paul _______________________________________________ Qemu-devel mailing list Qemu-devel@nongnu.org http://lists.nongnu.org/mailman/listinfo/qemu-devel
