On Sep 9, 2020, 23:20 +0530, Julia Suvorova <jus...@redhat.com>, wrote:
> On Fri, Sep 4, 2020 at 6:10 PM Ani Sinha <a...@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 <a...@anisinha.ca>
>
> Reviewed-by: Julia Suvorova <jus...@redhat.com>
>
> BTW, aren't all bridges handled in build_append_pci_bus_devices()
> cold-plugged?
Yes they are.
>
> > ---
> > 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
> >
>
