Re: Why set .suppress_bind_attrs even though .remove() implemented?

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On Mon, Jul 25, 2022 at 06:35:27PM +0100, Marc Zyngier wrote:

[...]

> > That is precisely the way I've been testing it and everything appears
> > to be tore down as it should.
> >
> > And a PCI driver that has been unbound should have released its
> > resources, or that's a driver bug. Right?
> 
> But that's the thing: you can easily remove part of the infrastructure
> without the endpoint driver even noticing. It may not happen in your
> particular case if removing the RC driver will also nuke the endpoints
> in the process, but I can't see this is an absolute guarantee. The
> crash pointed to by an earlier email is symptomatic of it.
> 
> > And for the OF INTx case you mentioned earlier, aren't those mapped by
> > PCI core and could in theory be released by core as well?
> 
> Potentially, though I haven't tried to follow the life cycle of those.
> The whole thing is pretty fragile, and this sort of resource is rarely
> expected to be removed...

This made me notice that we don't undo the actions (ie bridge->map_irq())
executed in pci_assign_irq() in pci_device_remove(); I don't think this
can be right and that's already a candidate for a fix.

It is not necessarily related to this thread topic, though I believe,
in an _ideal_ world, removing a bridge should guarantee that all
the downstream devices (ie drivers) had a chance of freeing/disposing
the resources they allocated. This in theory; I totally understand
Marc's point of view here and we should make up our mind about what
we want to do on host bridge removal policy - this will take me more
time to get to the bottom of it.

Lorenzo



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