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Re: [PATCH v2] i440fx/acpi: disable hotplug of cold plugged bridges rega
From: |
Philippe Mathieu-Daudé |
Subject: |
Re: [PATCH v2] i440fx/acpi: disable hotplug of cold plugged bridges regarldless of hotplug switch |
Date: |
Fri, 4 Sep 2020 15:29:19 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 |
Hi Ani,
On 9/4/20 2:44 PM, Ani Sinha wrote:
> Cold plugged bridges should not be hot unpluggable, even when their hotplug
> property (acpi-pci-hotplug-with-bridge-support) is turned off. 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. When devices are attached to the bridge, the bridge
> is ultimately not hot-unpluggable. 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-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.
Can you add a test reproducer?
Looking at tests/qtest/virtio-rng-test.c it shouldn't be that
hard / time consuming.
Thanks!
Phil.
>
> Signed-off-by: Ani Sinha <ani@anisinha.ca>
> ---
> hw/i386/acpi-build.c | 12 ++++++------
> 1 file changed, 6 insertions(+), 6 deletions(-)
>
> Changelog:
> v2: cosmetic commit log update.
> 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;
>