Re: [Qemu-devel] [PATCH] hw/pci: disable pci-bridge's shpc by default

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Nov 02, 2016 at 05:16:42PM +0200, Marcel Apfelbaum wrote:
> The shpc component is optional while  ACPI hotplug is used
> for hot-plugging PCI devices into a PCI-PCI bridge.
> Disabling the shpc by default will make slot 0 usable at boot time

at the cost of breaking all hotplug for all non-acpi users.

> and not only for hot-plug, without loosing any functionality.
> Older machines will have shpc enabled for compatibility reasons.
> 
> Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>

Is an extra slot such a big deal? You can always add more bridges ...

> ---
>  hw/pci-bridge/pci_bridge_dev.c | 2 +-
>  include/hw/compat.h            | 4 ++++
>  2 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/pci-bridge/pci_bridge_dev.c b/hw/pci-bridge/pci_bridge_dev.c
> index 5dbd933..647ad80 100644
> --- a/hw/pci-bridge/pci_bridge_dev.c
> +++ b/hw/pci-bridge/pci_bridge_dev.c
> @@ -163,7 +163,7 @@ static Property pci_bridge_dev_properties[] = {
>      DEFINE_PROP_ON_OFF_AUTO(PCI_BRIDGE_DEV_PROP_MSI, PCIBridgeDev, msi,
>                              ON_OFF_AUTO_AUTO),
>      DEFINE_PROP_BIT(PCI_BRIDGE_DEV_PROP_SHPC, PCIBridgeDev, flags,
> -                    PCI_BRIDGE_DEV_F_SHPC_REQ, true),
> +                    PCI_BRIDGE_DEV_F_SHPC_REQ, false),
>      DEFINE_PROP_END_OF_LIST(),
>  };
>  
> diff --git a/include/hw/compat.h b/include/hw/compat.h
> index 0f06e11..388b7ec 100644
> --- a/include/hw/compat.h
> +++ b/include/hw/compat.h
> @@ -18,6 +18,10 @@
>          .driver   = "intel-iommu",\
>          .property = "x-buggy-eim",\
>          .value    = "true",\
> +    },{\
> +        .driver   = "pci-bridge",\
> +        .property = "shpc",\
> +        .value    = "on",\
>      },
>  
>  #define HW_COMPAT_2_6 \
> -- 
> 2.5.5