Re: [PATCH 00/35] memory: QOM-ify AddressSpace

[Peter Xu <peterx@redhat.com>]

On Thu, Sep 18, 2025 at 09:47:07PM +0900, Akihiko Odaki wrote:
> On 2025/09/18 21:39, Cédric Le Goater wrote:
> > Hello Akihiko,
> > 
> > On 9/17/25 14:56, Akihiko Odaki wrote:
> > > Based-on: <20250917-subregion-v1-0-bef37d9b4f73@rsg.ci.i.u-tokyo.ac.jp>
> > > ("[PATCH 00/14] Fix memory region use-after-finalization")
> > > 
> > > Make AddressSpaces QOM objects to ensure that they are destroyed when
> > > their owners are finalized and also to get a unique path for debugging
> > > output.
> > > 
> > > Suggested by BALATON Zoltan:
> > > https://lore.kernel.org/qemu-devel/cd21698f-db77-eb75-6966-
> > > d559fdcab835@eik.bme.hu/
> > > 
> > > Signed-off-by: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
> > 
> > I wonder if this is going to fix an issue I was seeing a while ago
> > in the FSI models. I couldn't find a clean way to avoid corrupting
> > memory because of how the address_space was created and later on
> > destroyed. See below,
> 
> Partially, but this is insufficient.
> 
> The first problem is that AddressSpace suffers from circular references the
> following series solves:
> https://lore.kernel.org/qemu-devel/20250906-mr-v2-0-2820f5a3d282@rsg.ci.i.u-tokyo.ac.jp/
> "[PATCH v2 0/3] memory: Stop piggybacking on memory region owners"
> 
> Another problem is that RCU is not properly waited. This is left to future
> work.

Just to mention, Peter Maydell just posted a series for fixing AS
destructions here:

https://lore.kernel.org/qemu-devel/20250929144228.1994037-1-peter.maydell@linaro.org/

IIUC it should also work for FSI, if FSI can convert to use dynamically
allocated AddressSpaces (with/without QOMify; as Akihiko pointed out
correctly, these should be orthogonal), then provide a proper unrealize()
of the bus device to invoke address_space_destroy_free().

Thanks,

-- 
Peter Xu