Re: Hot unplug disabling on pci-pci bridge

[Igor Mammedov <imammedo@redhat.com>]

On Tue, 24 Mar 2020 13:29:10 +0000
Ani Sinha <ani.sinha@nutanix.com> wrote:

> On Mar 24, 2020, at 4:47 PM, Igor Mammedov <imammedo@redhat.com<mailto:imammedo@redhat.com>> wrote:
> 
> you probably have APCI hotplug for bridges enabled (which applies to
> all  cold-plugged bridges).
> You can disable it by setting following property
> -global PIIX4_PM.acpi-pci-hotplug-with-bridge-support=off
> then it should fall back to SHPC which are are tying to disable
> 
> Ok I patched to change the default :
> 
> ---
> hw/acpi/piix4.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/hw/acpi/piix4.c b/hw/acpi/piix4.c
> index d706360..db888cb 100644
> --- a/hw/acpi/piix4.c
> +++ b/hw/acpi/piix4.c
> @@ -675,7 +675,7 @@ static Property piix4_pm_properties[] = {
>     DEFINE_PROP_UINT8(ACPI_PM_PROP_S4_DISABLED, PIIX4PMState, disable_s4, 1),
>     DEFINE_PROP_UINT8(ACPI_PM_PROP_S4_VAL, PIIX4PMState, s4_val, 2),
>     DEFINE_PROP_BOOL("acpi-pci-hotplug-with-bridge-support", PIIX4PMState,
> -                     use_acpi_pci_hotplug, true),
> +                     use_acpi_pci_hotplug, false),
>     DEFINE_PROP_BOOL("memory-hotplug-support", PIIX4PMState,
>                      acpi_memory_hotplug.is_enabled, true),
>     DEFINE_PROP_END_OF_LIST(),
> --
> 1.9.4
> 
> This seems to work but now Windows is giving an option to eject pci bridges. Clicking it does not do anything. I wonder if we can disable that as well. AFAIK hot unplugging bridges would not take effect until ACPI tables are updated and the OS kernel re-reads the updated tables. See https://bugzilla.redhat.com/show_bug.cgi?id=1339875

if you are interested in hacking ACPI PCI hotplug more, look at how build_append_pci_bus_devices() works

> 
> Ani
> [cid:809BEDB4-EEF6-4197-A083-4AF2E9999CEB]