Cold plugged bridges are not hot unpluggable, even when their hotplug property (acpi-pci-hotplug-with-bridge-support) is turned off. Please see the function acpi_pcihp_pc_no_hotplug() (thanks Julia). However, with the current implementaton, windows would try to hot-unplug a pci bridge when it's hotplug switch is off. This is regardless of whether there are devices attached to the bridge. This is because we add amls like _EJ0 etc for the pci slot where the bridge is cold plugged. We have a demo video here: https://youtu.be/pME2sjyQweo
In this fix, we identify a cold plugged bridge and for cold plugged bridges, we do not add the appropriate amls and acpi methods that are used by the OS to identify a hot-pluggable/unpluggable pci device. After this change, Windows does not show an option to eject the PCI bridge. A demo video is here: https://youtu.be/kbgej5B9Hgs While at it, I have also updated a stale comment. This change is tested with a Windows 2012R2 guest image and Windows 2019 server guest image running on Ubuntu 18.04 host. This change is based off of upstream qemu master branch tag v5.1.0. Signed-off-by: Ani Sinha <[email protected]> --- hw/i386/acpi-build.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) changelog: v3: commit log updates providing more accurate information as received from Julia. v2: cosmetic commit log updates with patch testing information. v1: initial patch. diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c index b7bcbbbb2a..90b863f4ec 100644 --- a/hw/i386/acpi-build.c +++ b/hw/i386/acpi-build.c @@ -359,6 +359,7 @@ static void build_append_pci_bus_devices(Aml *parent_scope, PCIBus *bus, int slot = PCI_SLOT(i); bool hotplug_enabled_dev; bool bridge_in_acpi; + bool cold_plugged_bridge; if (!pdev) { if (bsel) { /* add hotplug slots for non present devices */ @@ -380,15 +381,14 @@ static void build_append_pci_bus_devices(Aml *parent_scope, PCIBus *bus, pc = PCI_DEVICE_GET_CLASS(pdev); dc = DEVICE_GET_CLASS(pdev); - /* When hotplug for bridges is enabled, bridges are - * described in ACPI separately (see build_pci_bus_end). - * In this case they aren't themselves hot-pluggable. + /* + * Cold plugged bridges aren't themselves hot-pluggable. * Hotplugged bridges *are* hot-pluggable. */ - bridge_in_acpi = pc->is_bridge && pcihp_bridge_en && - !DEVICE(pdev)->hotplugged; + cold_plugged_bridge = pc->is_bridge && !DEVICE(pdev)->hotplugged; + bridge_in_acpi = cold_plugged_bridge && pcihp_bridge_en; - hotplug_enabled_dev = bsel && dc->hotpluggable && !bridge_in_acpi; + hotplug_enabled_dev = bsel && dc->hotpluggable && !cold_plugged_bridge; if (pc->class_id == PCI_CLASS_BRIDGE_ISA) { continue; -- 2.17.1
