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Re: [PATCH v1] i440fx/acpi: don't hot-unplug cold plugged bridges when t
From: |
Ani Sinha |
Subject: |
Re: [PATCH v1] i440fx/acpi: don't hot-unplug cold plugged bridges when their hotplug switch is off |
Date: |
Fri, 4 Sep 2020 21:23:31 +0530 |
On Fri, Sep 4, 2020 at 9:18 PM Julia Suvorova <jusual@redhat.com> wrote:
>
> On Fri, Sep 4, 2020 at 10:25 AM Ani Sinha <ani@anisinha.ca> wrote:
> >
> > Cold plugged bridges should not be hot unpluggable, even when their hotplug
> > property
> > (acpi-pci-hotplug-with-bridge-support) is turned off.
>
> Unplugging a cold-plugged bridge is impossible already, see
> acpi_pcihp_pc_no_hotplug().
Ah cool. So all the more reason we should fix this because guest OSes
should not think that the device is hot-unpluggable.
>
> Best regards, Julia Suvorova.
>
> > 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 running on Ubuntu
> > host. This
> > change is based off of upstream qemu master branch tag v5.1.0.
> >
> > Signed-off-by: Ani Sinha <ani@anisinha.ca>
> > ---
> > hw/i386/acpi-build.c | 12 ++++++------
> > 1 file changed, 6 insertions(+), 6 deletions(-)
> >
> > 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
> >
>