Re: [PULL 06/13] Introduce a new flag for i440fx to disable PCI hotplug on the root bus

[Ani Sinha]

> On Aug 31, 2020, at 2:27 AM, Michael S. Tsirkin <mst@redhat.com> wrote:
> 
> On Thu, Aug 27, 2020 at 11:29:34PM +0530, Ani Sinha wrote:
>>> On Thu, Aug 27, 2020 at 11:11 PM Igor Mammedov <imammedo@redhat.com> wrote:
>>> 
>>> On Thu, 27 Aug 2020 09:40:34 -0400
>>> "Michael S. Tsirkin" <mst@redhat.com> wrote:
>>> 
>>>> From: Ani Sinha <ani@anisinha.ca>
>>>> 
>>>> We introduce a new global flag 'acpi-root-pci-hotplug' for i440fx with 
>>>> which
>>>> we can turn on or off PCI device hotplug on the root bus. This flag can be
>>>> used to prevent all PCI devices from getting hotplugged or unplugged from 
>>>> the
>>>> root PCI bus.
>>>> This feature is targetted mostly towards Windows VMs. It is useful in cases
>>>> where some hypervisor admins want to deploy guest VMs in a way so that the
>>>> users of the guest OSes are not able to hot-eject certain PCI devices from
>>>> the Windows system tray. Laine has explained the use case here in detail:
>>>> https://www.redhat.com/archives/libvir-list/2020-February/msg00110.html
>>>> 
>>>> Julia has resolved this issue for PCIE buses with the following commit:
>>>> 530a0963184e57e71a5b538 ("pcie_root_port: Add hotplug disabling option")
>>>> 
>>>> This commit attempts to introduce similar behavior for PCI root buses used 
>>>> in
>>>> i440fx machine types (although in this case, we do not have a per-slot
>>>> capability to turn hotplug on or off).
>>>> 
>>>> Usage:
>>>>   -global PIIX4_PM.acpi-root-pci-hotplug=off
>>>> 
>>>> By default, this option is enabled which means that hotplug is turned on 
>>>> for
>>>> the PCI root bus.
>>>> 
>>>> The previously existing flag 'acpi-pci-hotplug-with-bridge-support' for 
>>>> PCI-PCI
>>>> bridges remain as is and can be used along with this new flag to control 
>>>> PCI
>>>> hotplug on PCI bridges.
>>>> 
>>>> This change has been tested using a Windows 2012R2 server guest image and 
>>>> also
>>>> with a Windows 2019 server guest image on a Ubuntu 18.04 host using the 
>>>> latest
>>>> master qemu from upstream.
>>>> 
>>>> Signed-off-by: Ani Sinha <ani@anisinha.ca>
>>>> Message-Id: <20200821165403.26589-1-ani@anisinha.ca>
>>>> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
>>>> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
>>> 
>>> 
>>>> Tested-by: Igor Mammedov <imammedo@redhat.com>
>>>> Reviewed-by: Igor Mammedov <imammedo@redhat.com>
>>> A glitch in scripts?
>>> I didn't review nor tested this (v8) version
>> 
>> oops! I am so eager to get this done and dusted :)
> 
> 
> One thing I would like to see is that all of these flags
> should also disable the relevant functionality.

The flag that I introduced would with this patch along with the other patch I 
sent to address Julia's concern over ejecting root bus when bsel is absent.

> 
> 
> 
>>> 
>>>> ---
>>>> include/hw/acpi/pcihp.h |  2 +-
>>>> hw/acpi/pcihp.c         | 23 ++++++++++++++++++++++-
>>>> hw/acpi/piix4.c         |  5 ++++-
>>>> 3 files changed, 27 insertions(+), 3 deletions(-)
>>>> 
>>>> diff --git a/include/hw/acpi/pcihp.h b/include/hw/acpi/pcihp.h
>>>> index 8bc4a4c01d..02f4665767 100644
>>>> --- a/include/hw/acpi/pcihp.h
>>>> +++ b/include/hw/acpi/pcihp.h
>>>> @@ -67,7 +67,7 @@ void acpi_pcihp_device_unplug_request_cb(HotplugHandler 
>>>> *hotplug_dev,
>>>>                                          Error **errp);
>>>> 
>>>> /* Called on reset */
>>>> -void acpi_pcihp_reset(AcpiPciHpState *s);
>>>> +void acpi_pcihp_reset(AcpiPciHpState *s, bool acpihp_root_off);
>>>> 
>>>> extern const VMStateDescription vmstate_acpi_pcihp_pci_status;
>>>> 
>>>> diff --git a/hw/acpi/pcihp.c b/hw/acpi/pcihp.c
>>>> index 9e31ab2da4..39b1f74442 100644
>>>> --- a/hw/acpi/pcihp.c
>>>> +++ b/hw/acpi/pcihp.c
>>>> @@ -104,6 +104,24 @@ static void acpi_set_pci_info(void)
>>>>     }
>>>> }
>>>> 
>>>> +static void acpi_pcihp_disable_root_bus(void)
>>>> +{
>>>> +    static bool root_hp_disabled;
>>>> +    PCIBus *bus;
>>>> +
>>>> +    if (root_hp_disabled) {
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    bus = find_i440fx();
>>>> +    if (bus) {
>>>> +        /* setting the hotplug handler to NULL makes the bus 
>>>> non-hotpluggable */
>>>> +        qbus_set_hotplug_handler(BUS(bus), NULL);
>>>> +    }
>>>> +    root_hp_disabled = true;
>>>> +    return;
>>>> +}
>>>> +
>>>> static void acpi_pcihp_test_hotplug_bus(PCIBus *bus, void *opaque)
>>>> {
>>>>     AcpiPciHpFind *find = opaque;
>>>> @@ -209,8 +227,11 @@ static void acpi_pcihp_update(AcpiPciHpState *s)
>>>>     }
>>>> }
>>>> 
>>>> -void acpi_pcihp_reset(AcpiPciHpState *s)
>>>> +void acpi_pcihp_reset(AcpiPciHpState *s, bool acpihp_root_off)
>>>> {
>>>> +    if (acpihp_root_off) {
>>>> +        acpi_pcihp_disable_root_bus();
>>>> +    }
>>>>     acpi_set_pci_info();
>>>>     acpi_pcihp_update(s);
>>>> }
>>>> diff --git a/hw/acpi/piix4.c b/hw/acpi/piix4.c
>>>> index 26bac4f16c..e6163bb6ce 100644
>>>> --- a/hw/acpi/piix4.c
>>>> +++ b/hw/acpi/piix4.c
>>>> @@ -78,6 +78,7 @@ typedef struct PIIX4PMState {
>>>> 
>>>>     AcpiPciHpState acpi_pci_hotplug;
>>>>     bool use_acpi_hotplug_bridge;
>>>> +    bool use_acpi_root_pci_hotplug;
>>>> 
>>>>     uint8_t disable_s3;
>>>>     uint8_t disable_s4;
>>>> @@ -324,7 +325,7 @@ static void piix4_pm_reset(DeviceState *dev)
>>>>         pci_conf[0x5B] = 0x02;
>>>>     }
>>>>     pm_io_space_update(s);
>>>> -    acpi_pcihp_reset(&s->acpi_pci_hotplug);
>>>> +    acpi_pcihp_reset(&s->acpi_pci_hotplug, !s->use_acpi_root_pci_hotplug);
>>>> }
>>>> 
>>>> static void piix4_pm_powerdown_req(Notifier *n, void *opaque)
>>>> @@ -635,6 +636,8 @@ static Property piix4_pm_properties[] = {
>>>>     DEFINE_PROP_UINT8(ACPI_PM_PROP_S4_VAL, PIIX4PMState, s4_val, 2),
>>>>     DEFINE_PROP_BOOL("acpi-pci-hotplug-with-bridge-support", PIIX4PMState,
>>>>                      use_acpi_hotplug_bridge, true),
>>>> +    DEFINE_PROP_BOOL("acpi-root-pci-hotplug", PIIX4PMState,
>>>> +                     use_acpi_root_pci_hotplug, true),
>>>>     DEFINE_PROP_BOOL("memory-hotplug-support", PIIX4PMState,
>>>>                      acpi_memory_hotplug.is_enabled, true),
>>>>     DEFINE_PROP_END_OF_LIST(),
>>> 
>