Re: [PATCH 5/9] i440fx/acpi: do not add hotplug related amls for cold plugged bridges

[Igor Mammedov <imammedo@redhat.com>]

On Fri, 11 Sep 2020 23:37:51 +0530
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
> 
> As a result of the patch, the following are the changes to the DSDT ACPI table:
> 
> @@ -858,38 +858,33 @@
>                      Return (Zero)
>                  }
> 
>                  Method (_S2D, 0, NotSerialized)  // _S2D: S2 Device State
>                  {
>                      Return (Zero)
>                  }
> 
>                  Method (_S3D, 0, NotSerialized)  // _S3D: S3 Device State
>                  {
>                      Return (Zero)
>                  }
>              }
> 
>              Device (S18)
>              {
> -                Name (_SUN, 0x03)  // _SUN: Slot User Number
>                  Name (_ADR, 0x00030000)  // _ADR: Address
> -                Method (_EJ0, 1, NotSerialized)  // _EJx: Eject Device
> -                {
> -                    PCEJ (BSEL, _SUN)
> -                }
>              }
> 
>              Device (S20)
>              {
>                  Name (_SUN, 0x04)  // _SUN: Slot User Number
>                  Name (_ADR, 0x00040000)  // _ADR: Address
>                  Method (_EJ0, 1, NotSerialized)  // _EJx: Eject Device
>                  {
>                      PCEJ (BSEL, _SUN)
>                  }
>              }
> 
>              Device (S28)
>              {
>                  Name (_SUN, 0x05)  // _SUN: Slot User Number
>                  Name (_ADR, 0x00050000)  // _ADR: Address
> @@ -1148,37 +1143,32 @@
>                      PCEJ (BSEL, _SUN)
>                  }
>              }
> 
>              Device (SF8)
>              {
>                  Name (_SUN, 0x1F)  // _SUN: Slot User Number
>                  Name (_ADR, 0x001F0000)  // _ADR: Address
>                  Method (_EJ0, 1, NotSerialized)  // _EJx: Eject Device
>                  {
>                      PCEJ (BSEL, _SUN)
>                  }
>              }
> 
>              Method (DVNT, 2, NotSerialized)
>              {
> -                If ((Arg0 & 0x08))
> -                {
> -                    Notify (S18, Arg1)
> -                }
> -
>                  If ((Arg0 & 0x10))
>                  {
>                      Notify (S20, Arg1)
>                  }
> 
>                  If ((Arg0 & 0x20))
>                  {
>                      Notify (S28, Arg1)
>                  }
> 
>                  If ((Arg0 & 0x40))
>                  {
>                      Notify (S30, Arg1)
>                  }
> 
>                  If ((Arg0 & 0x80))
> 
> 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: Igor Mammedov <imammedo@redhat.com>

> ---
>  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 7a5a8b3521..e079b686f5 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;