Re: [Qemu-devel] [PATCH 11/22] i8259: Update IRQ state after reset

[Blue Swirl]

On Sun, Oct 2, 2011 at 4:39 PM, Avi Kivity <address@hidden> wrote:
> On 09/28/2011 09:01 PM, Blue Swirl wrote:
>>
>> On Wed, Sep 28, 2011 at 11:00 AM, Jan Kiszka<address@hidden>
>>  wrote:
>> >  As we clearly modify the PIC state on pic_reset, we also have to update
>> >  the IRQ output. This only happened on init so far. Apply this
>> >  consistently.
>>
>> Nack, IRQ lines shouldn't be touched on reset. The other side may not
>> be ready for receiving the interrupt change and qemu_irqs are
>> stateless anyway.
>>
>
> The way to fix it is two-phase reset:
>
> phase 1: reset internal state (-> move all outputs to reset values), don't
> sample inputs yet

This solves the problem of old state accidentally interfering with reset state.

> phase 2: allow sampling inputs

This could lead to incorrect state for complex networks. It would
still be better than what we have now.