Re: [PATCH 4/5] hw/arm/smmuv3: Move reset to exit phase

[Peter Xu <peterx@redhat.com>]

On Fri, Feb 07, 2025 at 04:58:39PM +0000, Peter Maydell wrote:
> (I wonder if we ought to suggest quiescing outstanding
> DMA in the enter phase? But it's probably easier to fix
> the iommus like this series does than try to get every
> dma-capable pci device to do something different.)

I wonder if we should provide some generic helper to register vIOMMU reset
callbacks, so that we'll be sure any vIOMMU model impl that will register
at exit() phase only, and do nothing during the initial two phases.  Then
we can put some rich comment on that helper on why.

Looks like it means the qemu reset model in the future can be a combination
of device tree (which resets depth-first) and the three phases model.  We
will start to use different approach to solve different problems.

Maybe after we settle our mind, we should update the reset document,
e.g. for device emulation developers, we need to be clear on where to
quiesce the DMAs, and it must not happen at exit().  Both all devices and
all iommu impls need to follow the rules to make it work like the plan.

Thanks,

-- 
Peter Xu