On Sep 10, 2020, 00:00 +0530, Ani Sinha <[email protected]>, wrote:
> On Sep 9, 2020, 23:20 +0530, Julia Suvorova <[email protected]>, wrote:
> > On Fri, Sep 4, 2020 at 6:10 PM Ani Sinha <[email protected]> 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 <[email protected]>
> >
> > Reviewed-by: Julia Suvorova <[email protected]>
> >
> > 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
> > >
> >
