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Re: [RFC 0/3] try to solve the DMA to MMIO issue
From: |
Peter Maydell |
Subject: |
Re: [RFC 0/3] try to solve the DMA to MMIO issue |
Date: |
Thu, 3 Sep 2020 12:19:37 +0100 |
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.
thanks
-- PMM
- [RFC 2/3] xhci: make the IO handler reentrant, (continued)
Re: [RFC 0/3] try to solve the DMA to MMIO issue, Peter Maydell, 2020/09/03
- Re: [RFC 0/3] try to solve the DMA to MMIO issue, Li Qiang, 2020/09/03
- Re: [RFC 0/3] try to solve the DMA to MMIO issue,
Peter Maydell <=
- Re: [RFC 0/3] try to solve the DMA to MMIO issue, Li Qiang, 2020/09/03
- Re: [RFC 0/3] try to solve the DMA to MMIO issue, Peter Maydell, 2020/09/03
- Re: [RFC 0/3] try to solve the DMA to MMIO issue, Philippe Mathieu-Daudé, 2020/09/03
- Re: [RFC 0/3] try to solve the DMA to MMIO issue, Peter Maydell, 2020/09/03
Re: [RFC 0/3] try to solve the DMA to MMIO issue, Jason Wang, 2020/09/03