Introduce a new flag for i440fx to disable PCI hotplug on the root bus

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 <[email protected]>
Message-Id: <20200821165403[email protected]>
Reviewed-by: Michael S. Tsirkin <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>
Tested-by: Igor Mammedov <[email protected]>
Reviewed-by: Igor Mammedov <[email protected]>

diff --git a/hw/acpi/pcihp.c b/hw/acpi/pcihp.c
index 9e31ab2da4d8ff10cb2cc70ee88f4d6798b9d835..39b1f74442783a273a8fa9ee001fef7ef7774fc8 100644 (file)
--- 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 26bac4f16c18a7d32b3821e5e3e67c9ff4150360..e6163bb6ce582bf28583e6737af4789ddf1241d9 100644 (file)
--- 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(),

diff --git a/include/hw/acpi/pcihp.h b/include/hw/acpi/pcihp.h
index 8bc4a4c01dba268625fe1f56f5b4757e00bee14c..02f466576725bca7137d2227e5910ffe6d227c3f 100644 (file)
--- 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;