On Thu, 3 Sep 2020 at 12:11, Li Qiang <liq3ea@gmail.com> wrote:
Peter Maydell <peter.maydell@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 <jasowang@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.
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.