Peter Maydell <peter.mayd...@linaro.org> 于2020年9月3日周四 下午7:19写道: > > On Thu, 3 Sep 2020 at 12:11, Li Qiang <liq...@gmail.com> wrote: > > > > Peter Maydell <peter.mayd...@linaro.org> 于2020年9月3日周四 下午6:53写道: > > > > > > On Thu, 3 Sep 2020 at 04:55, Jason Wang <jasow...@redhat.com> wrote: > > > > I think we still need to seek a way to address this issue completely. > > > > > > > > How about adding a flag in MemoryRegionOps and detect the reentrancy > > > > through that flag? > > > > > > This won't catch everything. Consider this situation: > > > Device A makes DMA access to device B > > > Device B's write-handling causes it to raise an > > > outbound qemu_irq signal > > > The qemu_irq signal is connected to device A > > > > Here mean device A is an interrupt controller? > > No. Any device can have an inbound or outbound qemu_irq line. > We use them not just for actual IRQ lines but for any > situation where we need to pass an on-or-off signal from > one device to another.
Could you please provide some example, I haven't noticed this before. Thanks. > > > This is special case I think. > > It's an example of why looking purely at MMIO is not > sufficient. We should prefer to see if we can come up with > a design principle that works for all between-device > coordination before we implement something that is specific > to MMIO. So first we may be define a clean boundary/interface between device coordination? Thanks, Li Qiang > > thanks > -- PMM