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

[Eric Auger <eric.auger@redhat.com>]

Hi Peter,

On 2/7/25 7:18 PM, Peter Maydell wrote:
> On Fri, 7 Feb 2025 at 17:48, Peter Xu <peterx@redhat.com> wrote:
>> 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.
> The tree of QOM devices (i.e. the one based on the qbus buses
> and rooted at the sysbus) resets depth-first, but it does so in
> three phases: first we traverse everything doing 'enter'; then
> we traverse everything doing 'hold'; then we traverse everything
> doing 'exit'. There *used* to be an awkward mix of some things
> being three-phase and some not, but we have now got rid of all
> of those so a system reset does a single three-phase reset run
> which resets everything.
Thank you Peter. This is reassuring. I will add such kind of description
in the commit msg/cover letter.

Eric
>
> -- PMM
>