On Sep 10, 2020, 00:00 +0530, Ani Sinha <ani@anisinha.ca>, wrote:
On Sep 9, 2020, 23:20 +0530, Julia Suvorova <jusual@redhat.com>, wrote:
On Fri, Sep 4, 2020 at 6:10 PM Ani Sinha <ani@anisinha.ca> wrote:
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 <ani@anisinha.ca>
Reviewed-by: Julia Suvorova <jusual@redhat.com>
BTW, aren't all bridges handled in build_append_pci_bus_devices() cold-plugged?
Yes they are.
Maybe as an improvement we can simply identify a bridge instead of a cold plugged bridge. However let’s have that improvement as a separate patch on top of this. Also let’s see what Igor thinks.
---
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