Re: [Qemu-devel] [PATCH 23/27] hw/core/or-irq: Support more than 16 inputs to an OR gate

[Peter Maydell]

On 30 May 2018 at 17:59, Paolo Bonzini <address@hidden> wrote:
> On 21/05/2018 17:02, Peter Maydell wrote:
>> On 21 May 2018 at 15:34, Paolo Bonzini <address@hidden> wrote:
>>> Why do the levels have to be migrated at all?  It should be enough if
>>> the IRQ level is either migrated manually, or restored (e.g. in
>>> post_save callbacks) through other data that is migrated.
>> This is standard behaviour for devices: they track their
>> inbound irq/gpio lines, and then that becomes internal state for
>> them that must be migrated.
>
> But or_irq's input are another device's outbound lines, so tracking them
> should not be necessary.  The other device would do it for or_irq.

There's no mechanism in qemu_irq for the destination end to ask
the source end about its current value. The information flow
is strictly one-way.

thanks
-- PMM