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hw/i386/acpi-build: Deny control on PCIe Native Hot-plug in _OSC
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>
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