Re: [PATCH V2] Add a new PIIX option to control PCI hot unplugging of devices on non-root buses

[Ani Sinha]

> On Apr 29, 2020, at 10:58 AM, Michael S. Tsirkin <address@hidden> wrote:
> 
> For example, how about hot-plugging a bridge which doesn't
> support hotplug itself?

So now for every device we want to hot plug, we will add a new bridge? Sounds 
not a scalable and elegant idea.

> Would that happen to make windows
> do what you want, for both PCI and PCIE? We don't support
> hotplugging bridges with devices behind them ATM, but
> that sounds like a useful option.
> 
> 
> Also, pcie root ports recently gained ability to disable hotplug, see
>       commit 530a0963184e57e71a5b538e9161f115df533e96
>       Author: Julia Suvorova <address@hidden>
>       Date:   Wed Feb 26 18:46:07 2020 +0100
> 
>           pcie_root_port: Add hotplug disabling option
> 
> adding this to pci and pcie bridges sounds very reasonable.

This patch uses PCIE native hot plug capability to turn on or turn off per slot 
hot plug option. This does not enable hot unplugging while allowing devices to 
be hot plugged on a PCIE port. Besides, PCI-PCI bridges already have an option 
to disable hot plug capability for all the slots of that bridge. My patch 
follows that approach.