Re: [RFC 1/4] memory: add memory_region_init_io_with_dev interface

[Alexander Bulekov]

On 200909 1258, Li Qiang wrote:
> Gerd Hoffmann <kraxel@redhat.com> 于2020年9月9日周三 下午12:49写道：
> >
> > On Wed, Sep 09, 2020 at 10:15:47AM +0800, Jason Wang wrote:
> > >
> > > On 2020/9/9 上午12:41, Li Qiang wrote:
> > > > Currently the MR is not explicitly connecting with its device instead of
> > > > a opaque. In most situation this opaque is the deivce but it is not an
> > > > enforcement. This patch adds a DeviceState member of to MemoryRegion
> > > > we will use it in later patch.
> > >
> > >
> > > I don't have a deep investigation. But I wonder whether we could make sure
> > > of owner instead of adding a new field here.
> >
> > Should be possible.  There is object_dynamic_cast() which can be used to
> > figure whenever a given owner object is a device.
> >
> 
> I found most caller of 'memory_region_init_io' will set the owner to
> the device object.
> But some of them will just set it to NULL. Do will have a clear rule
> that the device's MR
> 'owner' should be the device object? If yes, we can use this field.
> 

Those seem to be devices that havent't been QOM-imfied yet?  Maybe those
devices are unlikely to be affected by these issues, though... 

For i386, it seems like parallel, port80, portF0, pckbd, and xen_pvdevice .. ?
I'm guessing none of these do DMA.

+CC Stefan, since he replied to the other thread.

> Thanks,
> Li Qiang
> 
> > take care,
> >   Gerd
> >