Re: [PATCH v3] i440fx/acpi: do not add hotplug related amls for cold plugged bridges

[Ani Sinha]

On Fri, Sep 11, 2020 at 9:45 PM Ani Sinha <ani@anisinha.ca> wrote:
>
> On Fri, Sep 11, 2020 at 9:39 PM Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > On Fri, Sep 11, 2020 at 09:35:42PM +0530, Ani Sinha wrote:
> > > On Fri, Sep 11, 2020 at 9:22 PM Michael S. Tsirkin <mst@redhat.com> wrote:
> > > >
> > > > On Thu, Sep 10, 2020 at 12:19:19AM +0530, Ani Sinha wrote:
> > > > > 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.
> > > >
> > > > Well this changes acpi tables so I don't see how this will pass
> > > > the unit tests. Did you test this change?
> > >
> > > There were no unit tests to cover this bridge flag. I have added the
> > > unit tests. It's the same one you have queued.
> >
> >
> > Hmm. somehow the new tests fail for me ...
>
> Maybe you need to pull this change out, make sure the tests passes and
> then apply it again:
>
> commit b26b2241baefc51fe2069b83cea9cfa654e75a43 (HEAD -> v5.1.0)
> Author: Ani Sinha <ani@anisinha.ca>
> Date:   Tue Sep 1 15:19:22 2020 +0530
>
>     piix4: don't reserve hw resources when hotplug is off globally
>
>     When acpi hotplug is turned off for both root pci bus as well as for pci
>     bridges, we should not generate the related amls for DSDT table or
> initialize
>     related hw ports or reserve hw resources. This change makes sure all those
>     operations are turned off in the case acpi pci hotplug is off globally.
>
>     Signed-off-by: Ani Sinha <ani@anisinha.ca>

For this patch, I have not sent any updated unit tests.

>
>
> >
> > > >
> > > >
> > > > >
> > > > >
> > > > >
> > > > >             ---
> > > > >
> > > > >             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
> > > > >
> > > > >
> > > > >
> > > > >
> > > > >
> > > >
> >