There are two ways to enable ACPI PCI Hot-plug:
* Disable the Hot-plug Capable bit on PCIe slots.
This was the first approach which led to regression [1-2], as
I/O space for a port is allocated only when it is hot-pluggable,
which is determined by HPC bit.
* Leave the HPC bit on and disable PCIe Native Hot-plug in _OSC
method.
This removes the (future) ability of hot-plugging switches with PCIe
Native hotplug since ACPI PCI Hot-plug only works with cold-plugged
bridges. If the user wants to explicitely use this feature, they can
disable ACPI PCI Hot-plug with:
--global ICH9-LPC.acpi-pci-hotplug-with-bridge-support=off
Change the bit in _OSC method so that the OS selects ACPI PCI Hot-plug
instead of PCIe Native.
[1] https://gitlab.com/qemu-project/qemu/-/issues/641
[2] https://bugzilla.redhat.com/show_bug.cgi?id=2006409
Signed-off-by: Julia Suvorova <jusual@redhat.com>
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20211112110857.3116853-5-imammedo@redhat.com>
Reviewed-by: Ani Sinha <ani@anisinha.ca>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
211afe5c69