On 05/17/2010 11:27 AM, Markus Armbruster wrote:
A slot is the hotpluggable entity. Open your computer and you can
actually see them.
QEMU doesn't really know that.
How can that be? Do we signal hotplug notifications to a function or
to a slot?
Can we hotplug a single function in an already occupied slot?
What I meant to say: we have no concept of "slot" in the higher level
interfaces, we have only bus and device.
If a PCI device has multiple functions, we have a separate qdev device
for each function. You can't unplug a "slot" (concept doesn't exist in
qdev), only a qdev device. Naturally, when you unplug a qdev device,
all functions in the same PCI slot need to go. This happens deep down
in the bowels of ACPI, in piix4_device_hotplug(). qdev is not aware of
this magic relation between the qdev devices for functions in the same
slot.
IMO, that's a serious bug. A slot is a user visible entity, both in
that devices can only be hotplugged only as slots, not functions, and
to determine the maximum number of devices you can add. If the user
knows about it, qemu should too.
We can easily represent a slot/device as a qbus with each of the
functions as devices attached to it.