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Re: [PATCH v7] xen/pt: reserve PCI slot 2 for Intel igd-passthru
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From: |
Michael S. Tsirkin |
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Subject: |
Re: [PATCH v7] xen/pt: reserve PCI slot 2 for Intel igd-passthru |
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Date: |
Mon, 9 Jan 2023 17:33:23 -0500 |
On Mon, Jan 09, 2023 at 04:55:42PM -0500, Chuck Zmudzinski wrote:
> Intel specifies that the Intel IGD must occupy slot 2 on the PCI bus,
> as noted in docs/igd-assign.txt in the Qemu source code.
>
> Currently, when the xl toolstack is used to configure a Xen HVM guest with
> Intel IGD passthrough to the guest with the Qemu upstream device model,
> a Qemu emulated PCI device will occupy slot 2 and the Intel IGD will occupy
> a different slot. This problem often prevents the guest from booting.
>
> The only available workaround is not good: Configure Xen HVM guests to use
> the old and no longer maintained Qemu traditional device model available
> from xenbits.xen.org which does reserve slot 2 for the Intel IGD.
>
> To implement this feature in the Qemu upstream device model for Xen HVM
> guests, introduce the following new functions, types, and macros:
>
> * XEN_PT_DEVICE_CLASS declaration, based on the existing TYPE_XEN_PT_DEVICE
> * XEN_PT_DEVICE_GET_CLASS macro helper function for XEN_PT_DEVICE_CLASS
> * typedef XenPTQdevRealize function pointer
> * XEN_PCI_IGD_SLOT_MASK, the value of slot_reserved_mask to reserve slot 2
> * xen_igd_reserve_slot and xen_igd_clear_slot functions
>
> The new xen_igd_reserve_slot function uses the existing slot_reserved_mask
> member of PCIBus to reserve PCI slot 2 for Xen HVM guests configured using
> the xl toolstack with the gfx_passthru option enabled, which sets the
> igd-passthru=on option to Qemu for the Xen HVM machine type.
I don't like how slot_reserved_mask is set initially then cleared on
device realize.
To me this looks like a fragile hack. I suggest one of the following
1. adding a new mask
"slot-manual-mask" or some such blocking auto-allocation of a given
slot without blocking its use if address is specified on command line.
2. adding a special property that overrides slot_reserved_mask
for a given device.
both need changes in pci core but look like something generally
useful.
>
> The new xen_igd_reserve_slot function also needs to be implemented in
> hw/xen/xen_pt_stub.c to prevent FTBFS during the link stage for the case
> when Qemu is configured with --enable-xen and --disable-xen-pci-passthrough,
> in which case it does nothing.
>
> The new xen_igd_clear_slot function overrides qdev->realize of the parent
> PCI device class to enable the Intel IGD to occupy slot 2 on the PCI bus
> since slot 2 was reserved by xen_igd_reserve_slot when the PCI bus was
> created in hw/i386/pc_piix.c for the case when igd-passthru=on.
>
> Move the call to xen_host_pci_device_get, and the associated error
> handling, from xen_pt_realize to the new xen_igd_clear_slot function to
> initialize the device class and vendor values which enables the checks for
> the Intel IGD to succeed. The verification that the host device is an
> Intel IGD to be passed through is done by checking the domain, bus, slot,
> and function values as well as by checking that gfx_passthru is enabled,
> the device class is VGA, and the device vendor in Intel.
>
> Signed-off-by: Chuck Zmudzinski <brchuckz@aol.com>
> ---
> Notes that might be helpful to reviewers of patched code in hw/xen:
>
> The new functions and types are based on recommendations from Qemu docs:
> https://qemu.readthedocs.io/en/latest/devel/qom.html
>
> Notes that might be helpful to reviewers of patched code in hw/i386:
>
> The small patch to hw/i386/pc_piix.c is protected by CONFIG_XEN so it does
> not affect builds that do not have CONFIG_XEN defined.
>
> xen_igd_gfx_pt_enabled() in the patched hw/i386/pc_piix.c file is an
> existing function that is only true when Qemu is built with
> xen-pci-passthrough enabled and the administrator has configured the Xen
> HVM guest with Qemu's igd-passthru=on option.
>
> v2: Remove From: <email address> tag at top of commit message
>
> v3: Changed the test for the Intel IGD in xen_igd_clear_slot:
>
> if (is_igd_vga_passthrough(&s->real_device) &&
> (s->real_device.vendor_id == PCI_VENDOR_ID_INTEL)) {
>
> is changed to
>
> if (xen_igd_gfx_pt_enabled() && (s->hostaddr.slot == 2)
> && (s->hostaddr.function == 0)) {
>
> I hoped that I could use the test in v2, since it matches the
> other tests for the Intel IGD in Qemu and Xen, but those tests
> do not work because the necessary data structures are not set with
> their values yet. So instead use the test that the administrator
> has enabled gfx_passthru and the device address on the host is
> 02.0. This test does detect the Intel IGD correctly.
>
> v4: Use brchuckz@aol.com instead of brchuckz@netscape.net for the author's
> email address to match the address used by the same author in commits
> be9c61da and c0e86b76
>
> Change variable for XEN_PT_DEVICE_CLASS: xptc changed to xpdc
>
> v5: The patch of xen_pt.c was re-worked to allow a more consistent test
> for the Intel IGD that uses the same criteria as in other places.
> This involved moving the call to xen_host_pci_device_get from
> xen_pt_realize to xen_igd_clear_slot and updating the checks for the
> Intel IGD in xen_igd_clear_slot:
>
> if (xen_igd_gfx_pt_enabled() && (s->hostaddr.slot == 2)
> && (s->hostaddr.function == 0)) {
>
> is changed to
>
> if (is_igd_vga_passthrough(&s->real_device) &&
> s->real_device.domain == 0 && s->real_device.bus == 0 &&
> s->real_device.dev == 2 && s->real_device.func == 0 &&
> s->real_device.vendor_id == PCI_VENDOR_ID_INTEL) {
>
> Added an explanation for the move of xen_host_pci_device_get from
> xen_pt_realize to xen_igd_clear_slot to the commit message.
>
> Rebase.
>
> v6: Fix logging by removing these lines from the move from xen_pt_realize
> to xen_igd_clear_slot that was done in v5:
>
> XEN_PT_LOG(d, "Assigning real physical device %02x:%02x.%d"
> " to devfn 0x%x\n",
> s->hostaddr.bus, s->hostaddr.slot, s->hostaddr.function,
> s->dev.devfn);
>
> This log needs to be in xen_pt_realize because s->dev.devfn is not
> set yet in xen_igd_clear_slot.
>
> v7: Inhibit out of context log message and needless processing by
> adding 2 lines at the top of the new xen_igd_clear_slot function:
>
> if (!(pci_bus->slot_reserved_mask & XEN_PCI_IGD_SLOT_MASK))
> return;
>
> Rebase. This removed an unnecessary header file from xen_pt.h
>
> hw/i386/pc_piix.c | 127 ++++++++++++++++++++++++++++++++-----------
> hw/xen/xen_pt.c | 49 ++++++++++++++---
> hw/xen/xen_pt.h | 16 ++++++
> hw/xen/xen_pt_stub.c | 4 ++
> 4 files changed, 154 insertions(+), 42 deletions(-)
>
> diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
> index b48047f50c..34a9736b5e 100644
> --- a/hw/i386/pc_piix.c
> +++ b/hw/i386/pc_piix.c
> @@ -32,6 +32,7 @@
> #include "hw/i386/pc.h"
> #include "hw/i386/apic.h"
> #include "hw/pci-host/i440fx.h"
> +#include "hw/rtc/mc146818rtc.h"
> #include "hw/southbridge/piix.h"
> #include "hw/display/ramfb.h"
> #include "hw/firmware/smbios.h"
> @@ -40,16 +41,16 @@
> #include "hw/usb.h"
> #include "net/net.h"
> #include "hw/ide/pci.h"
> -#include "hw/ide/piix.h"
> #include "hw/irq.h"
> #include "sysemu/kvm.h"
> #include "hw/kvm/clock.h"
> #include "hw/sysbus.h"
> +#include "hw/i2c/i2c.h"
> #include "hw/i2c/smbus_eeprom.h"
> #include "hw/xen/xen-x86.h"
> +#include "hw/xen/xen.h"
> #include "exec/memory.h"
> #include "hw/acpi/acpi.h"
> -#include "hw/acpi/piix4.h"
> #include "qapi/error.h"
> #include "qemu/error-report.h"
> #include "sysemu/xen.h"
> @@ -66,6 +67,7 @@
> #include "kvm/kvm-cpu.h"
>
> #define MAX_IDE_BUS 2
> +#define XEN_IOAPIC_NUM_PIRQS 128ULL
>
> #ifdef CONFIG_IDE_ISA
> static const int ide_iobase[MAX_IDE_BUS] = { 0x1f0, 0x170 };
> @@ -73,6 +75,32 @@ static const int ide_iobase2[MAX_IDE_BUS] = { 0x3f6, 0x376
> };
> static const int ide_irq[MAX_IDE_BUS] = { 14, 15 };
> #endif
>
> +/*
> + * Return the global irq number corresponding to a given device irq
> + * pin. We could also use the bus number to have a more precise mapping.
> + */
> +static int pci_slot_get_pirq(PCIDevice *pci_dev, int pci_intx)
> +{
> + int slot_addend;
> + slot_addend = PCI_SLOT(pci_dev->devfn) - 1;
> + return (pci_intx + slot_addend) & 3;
> +}
> +
> +static void piix_intx_routing_notifier_xen(PCIDevice *dev)
> +{
> + int i;
> +
> + /* Scan for updates to PCI link routes (0x60-0x63). */
> + for (i = 0; i < PIIX_NUM_PIRQS; i++) {
> + uint8_t v = dev->config_read(dev, PIIX_PIRQCA + i, 1);
> + if (v & 0x80) {
> + v = 0;
> + }
> + v &= 0xf;
> + xen_set_pci_link_route(i, v);
> + }
> +}
> +
> /* PC hardware initialisation */
> static void pc_init1(MachineState *machine,
> const char *host_type, const char *pci_type)
> @@ -84,7 +112,7 @@ static void pc_init1(MachineState *machine,
> MemoryRegion *system_io = get_system_io();
> PCIBus *pci_bus;
> ISABus *isa_bus;
> - int piix3_devfn = -1;
> + Object *piix4_pm;
> qemu_irq smi_irq;
> GSIState *gsi_state;
> BusState *idebus[MAX_IDE_BUS];
> @@ -205,10 +233,9 @@ static void pc_init1(MachineState *machine,
> gsi_state = pc_gsi_create(&x86ms->gsi, pcmc->pci_enabled);
>
> if (pcmc->pci_enabled) {
> - PIIX3State *piix3;
> + DeviceState *dev;
> PCIDevice *pci_dev;
> - const char *type = xen_enabled() ? TYPE_PIIX3_XEN_DEVICE
> - : TYPE_PIIX3_DEVICE;
> + int i;
>
> pci_bus = i440fx_init(pci_type,
> i440fx_host,
> @@ -216,21 +243,65 @@ static void pc_init1(MachineState *machine,
> x86ms->below_4g_mem_size,
> x86ms->above_4g_mem_size,
> pci_memory, ram_memory);
> + pci_bus_map_irqs(pci_bus,
> + xen_enabled() ? xen_pci_slot_get_pirq
> + : pci_slot_get_pirq);
> pcms->bus = pci_bus;
>
> - pci_dev = pci_create_simple_multifunction(pci_bus, -1, true, type);
> - piix3 = PIIX3_PCI_DEVICE(pci_dev);
> - piix3->pic = x86ms->gsi;
> - piix3_devfn = piix3->dev.devfn;
> - isa_bus = ISA_BUS(qdev_get_child_bus(DEVICE(piix3), "isa.0"));
> + pci_dev = pci_new_multifunction(-1, true, TYPE_PIIX3_DEVICE);
> + object_property_set_bool(OBJECT(pci_dev), "has-usb",
> + machine_usb(machine), &error_abort);
> + object_property_set_bool(OBJECT(pci_dev), "has-acpi",
> + x86_machine_is_acpi_enabled(x86ms),
> + &error_abort);
> + qdev_prop_set_uint32(DEVICE(pci_dev), "smb_io_base", 0xb100);
> + object_property_set_bool(OBJECT(pci_dev), "smm-enabled",
> + x86_machine_is_smm_enabled(x86ms),
> + &error_abort);
> + pci_realize_and_unref(pci_dev, pci_bus, &error_fatal);
> +
> + if (xen_enabled()) {
> + pci_device_set_intx_routing_notifier(
> + pci_dev, piix_intx_routing_notifier_xen);
> +
> + /*
> + * Xen supports additional interrupt routes from the PCI devices
> to
> + * the IOAPIC: the four pins of each PCI device on the bus are
> also
> + * connected to the IOAPIC directly.
> + * These additional routes can be discovered through ACPI.
> + */
> + pci_bus_irqs(pci_bus, xen_intx_set_irq, pci_dev,
> + XEN_IOAPIC_NUM_PIRQS);
> + }
> +
> + dev = DEVICE(object_resolve_path_component(OBJECT(pci_dev), "pic"));
> + for (i = 0; i < ISA_NUM_IRQS; i++) {
> + qdev_connect_gpio_out(dev, i, x86ms->gsi[i]);
> + }
> + isa_bus = ISA_BUS(qdev_get_child_bus(DEVICE(pci_dev), "isa.0"));
> + rtc_state = ISA_DEVICE(object_resolve_path_component(OBJECT(pci_dev),
> + "rtc"));
> + piix4_pm = object_resolve_path_component(OBJECT(pci_dev), "pm");
> + dev = DEVICE(object_resolve_path_component(OBJECT(pci_dev), "ide"));
> + pci_ide_create_devs(PCI_DEVICE(dev));
> + idebus[0] = qdev_get_child_bus(dev, "ide.0");
> + idebus[1] = qdev_get_child_bus(dev, "ide.1");
> } else {
> pci_bus = NULL;
> + piix4_pm = NULL;
> isa_bus = isa_bus_new(NULL, get_system_memory(), system_io,
> &error_abort);
> + isa_bus_irqs(isa_bus, x86ms->gsi);
> +
> + rtc_state = isa_new(TYPE_MC146818_RTC);
> + qdev_prop_set_int32(DEVICE(rtc_state), "base_year", 2000);
> + isa_realize_and_unref(rtc_state, isa_bus, &error_fatal);
> +
> i8257_dma_init(isa_bus, 0);
> pcms->hpet_enabled = false;
> + idebus[0] = NULL;
> + idebus[1] = NULL;
> }
> - isa_bus_irqs(isa_bus, x86ms->gsi);
>
> if (x86ms->pic == ON_OFF_AUTO_ON || x86ms->pic == ON_OFF_AUTO_AUTO) {
> pc_i8259_create(isa_bus, gsi_state->i8259_irq);
> @@ -252,18 +323,12 @@ static void pc_init1(MachineState *machine,
> }
>
> /* init basic PC hardware */
> - pc_basic_device_init(pcms, isa_bus, x86ms->gsi, &rtc_state, true,
> + pc_basic_device_init(pcms, isa_bus, x86ms->gsi, rtc_state, true,
> 0x4);
>
> pc_nic_init(pcmc, isa_bus, pci_bus);
>
> if (pcmc->pci_enabled) {
> - PCIDevice *dev;
> -
> - dev = pci_create_simple(pci_bus, piix3_devfn + 1, TYPE_PIIX3_IDE);
> - pci_ide_create_devs(dev);
> - idebus[0] = qdev_get_child_bus(&dev->qdev, "ide.0");
> - idebus[1] = qdev_get_child_bus(&dev->qdev, "ide.1");
> pc_cmos_init(pcms, idebus[0], idebus[1], rtc_state);
> }
> #ifdef CONFIG_IDE_ISA
> @@ -289,21 +354,9 @@ static void pc_init1(MachineState *machine,
> }
> #endif
>
> - if (pcmc->pci_enabled && machine_usb(machine)) {
> - pci_create_simple(pci_bus, piix3_devfn + 2, "piix3-usb-uhci");
> - }
> -
> - if (pcmc->pci_enabled && x86_machine_is_acpi_enabled(X86_MACHINE(pcms)))
> {
> - PCIDevice *piix4_pm;
> -
> + if (piix4_pm) {
> smi_irq = qemu_allocate_irq(pc_acpi_smi_interrupt, first_cpu, 0);
> - piix4_pm = pci_new(piix3_devfn + 3, TYPE_PIIX4_PM);
> - qdev_prop_set_uint32(DEVICE(piix4_pm), "smb_io_base", 0xb100);
> - qdev_prop_set_bit(DEVICE(piix4_pm), "smm-enabled",
> - x86_machine_is_smm_enabled(x86ms));
> - pci_realize_and_unref(piix4_pm, pci_bus, &error_fatal);
>
> - qdev_connect_gpio_out(DEVICE(piix4_pm), 0, x86ms->gsi[9]);
> qdev_connect_gpio_out_named(DEVICE(piix4_pm), "smi-irq", 0, smi_irq);
> pcms->smbus = I2C_BUS(qdev_get_child_bus(DEVICE(piix4_pm), "i2c"));
> /* TODO: Populate SPD eeprom data. */
> @@ -315,7 +368,7 @@ static void pc_init1(MachineState *machine,
> object_property_allow_set_link,
> OBJ_PROP_LINK_STRONG);
> object_property_set_link(OBJECT(machine),
> PC_MACHINE_ACPI_DEVICE_PROP,
> - OBJECT(piix4_pm), &error_abort);
> + piix4_pm, &error_abort);
> }
>
> if (machine->nvdimms_state->is_enabled) {
> @@ -405,6 +458,9 @@ static void pc_xen_hvm_init(MachineState *machine)
> }
>
> pc_xen_hvm_init_pci(machine);
> + if (xen_igd_gfx_pt_enabled()) {
> + xen_igd_reserve_slot(pcms->bus);
> + }
> pci_create_simple(pcms->bus, -1, "xen-platform");
> }
> #endif
> @@ -441,6 +497,11 @@ static void pc_i440fx_8_0_machine_options(MachineClass
> *m)
> pc_i440fx_machine_options(m);
> m->alias = "pc";
> m->is_default = true;
> +#ifdef CONFIG_MICROVM_DEFAULT
> + m->is_default = false;
> +#else
> + m->is_default = true;
> +#endif
> }
>
> DEFINE_I440FX_MACHINE(v8_0, "pc-i440fx-8.0", NULL,
> diff --git a/hw/xen/xen_pt.c b/hw/xen/xen_pt.c
> index 0ec7e52183..eff38155ef 100644
> --- a/hw/xen/xen_pt.c
> +++ b/hw/xen/xen_pt.c
> @@ -780,15 +780,6 @@ static void xen_pt_realize(PCIDevice *d, Error **errp)
> s->hostaddr.bus, s->hostaddr.slot, s->hostaddr.function,
> s->dev.devfn);
>
> - xen_host_pci_device_get(&s->real_device,
> - s->hostaddr.domain, s->hostaddr.bus,
> - s->hostaddr.slot, s->hostaddr.function,
> - errp);
> - if (*errp) {
> - error_append_hint(errp, "Failed to \"open\" the real pci device");
> - return;
> - }
> -
> s->is_virtfn = s->real_device.is_virtfn;
> if (s->is_virtfn) {
> XEN_PT_LOG(d, "%04x:%02x:%02x.%d is a SR-IOV Virtual Function\n",
> @@ -950,11 +941,50 @@ static void xen_pci_passthrough_instance_init(Object
> *obj)
> PCI_DEVICE(obj)->cap_present |= QEMU_PCI_CAP_EXPRESS;
> }
>
> +void xen_igd_reserve_slot(PCIBus *pci_bus)
> +{
> + XEN_PT_LOG(0, "Reserving PCI slot 2 for IGD\n");
> + pci_bus->slot_reserved_mask |= XEN_PCI_IGD_SLOT_MASK;
> +}
> +
> +static void xen_igd_clear_slot(DeviceState *qdev, Error **errp)
> +{
> + ERRP_GUARD();
> + PCIDevice *pci_dev = (PCIDevice *)qdev;
> + XenPCIPassthroughState *s = XEN_PT_DEVICE(pci_dev);
> + XenPTDeviceClass *xpdc = XEN_PT_DEVICE_GET_CLASS(s);
> + PCIBus *pci_bus = pci_get_bus(pci_dev);
> +
> + if (!(pci_bus->slot_reserved_mask & XEN_PCI_IGD_SLOT_MASK))
> + return;
> +
> + xen_host_pci_device_get(&s->real_device,
> + s->hostaddr.domain, s->hostaddr.bus,
> + s->hostaddr.slot, s->hostaddr.function,
> + errp);
> + if (*errp) {
> + error_append_hint(errp, "Failed to \"open\" the real pci device");
> + return;
> + }
> +
> + if (is_igd_vga_passthrough(&s->real_device) &&
> + s->real_device.domain == 0 && s->real_device.bus == 0 &&
> + s->real_device.dev == 2 && s->real_device.func == 0 &&
> + s->real_device.vendor_id == PCI_VENDOR_ID_INTEL) {
> + pci_bus->slot_reserved_mask &= ~XEN_PCI_IGD_SLOT_MASK;
> + XEN_PT_LOG(pci_dev, "Intel IGD found, using slot 2\n");
> + }
> + xpdc->pci_qdev_realize(qdev, errp);
> +}
> +
> static void xen_pci_passthrough_class_init(ObjectClass *klass, void *data)
> {
> DeviceClass *dc = DEVICE_CLASS(klass);
> PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
>
> + XenPTDeviceClass *xpdc = XEN_PT_DEVICE_CLASS(klass);
> + xpdc->pci_qdev_realize = dc->realize;
> + dc->realize = xen_igd_clear_slot;
> k->realize = xen_pt_realize;
> k->exit = xen_pt_unregister_device;
> k->config_read = xen_pt_pci_read_config;
> @@ -977,6 +1007,7 @@ static const TypeInfo xen_pci_passthrough_info = {
> .instance_size = sizeof(XenPCIPassthroughState),
> .instance_finalize = xen_pci_passthrough_finalize,
> .class_init = xen_pci_passthrough_class_init,
> + .class_size = sizeof(XenPTDeviceClass),
> .instance_init = xen_pci_passthrough_instance_init,
> .interfaces = (InterfaceInfo[]) {
> { INTERFACE_CONVENTIONAL_PCI_DEVICE },
> diff --git a/hw/xen/xen_pt.h b/hw/xen/xen_pt.h
> index cf10fc7bbf..8c25932b4b 100644
> --- a/hw/xen/xen_pt.h
> +++ b/hw/xen/xen_pt.h
> @@ -2,6 +2,7 @@
> #define XEN_PT_H
>
> #include "hw/xen/xen_common.h"
> +#include "hw/pci/pci_bus.h"
> #include "xen-host-pci-device.h"
> #include "qom/object.h"
>
> @@ -40,7 +41,20 @@ typedef struct XenPTReg XenPTReg;
> #define TYPE_XEN_PT_DEVICE "xen-pci-passthrough"
> OBJECT_DECLARE_SIMPLE_TYPE(XenPCIPassthroughState, XEN_PT_DEVICE)
>
> +#define XEN_PT_DEVICE_CLASS(klass) \
> + OBJECT_CLASS_CHECK(XenPTDeviceClass, klass, TYPE_XEN_PT_DEVICE)
> +#define XEN_PT_DEVICE_GET_CLASS(obj) \
> + OBJECT_GET_CLASS(XenPTDeviceClass, obj, TYPE_XEN_PT_DEVICE)
> +
> +typedef void (*XenPTQdevRealize)(DeviceState *qdev, Error **errp);
> +
> +typedef struct XenPTDeviceClass {
> + PCIDeviceClass parent_class;
> + XenPTQdevRealize pci_qdev_realize;
> +} XenPTDeviceClass;
> +
> uint32_t igd_read_opregion(XenPCIPassthroughState *s);
> +void xen_igd_reserve_slot(PCIBus *pci_bus);
> void igd_write_opregion(XenPCIPassthroughState *s, uint32_t val);
> void xen_igd_passthrough_isa_bridge_create(XenPCIPassthroughState *s,
> XenHostPCIDevice *dev);
> @@ -75,6 +89,8 @@ typedef int (*xen_pt_conf_byte_read)
>
> #define XEN_PCI_INTEL_OPREGION 0xfc
>
> +#define XEN_PCI_IGD_SLOT_MASK 0x4UL /* Intel IGD slot_reserved_mask */
> +
> typedef enum {
> XEN_PT_GRP_TYPE_HARDWIRED = 0, /* 0 Hardwired reg group */
> XEN_PT_GRP_TYPE_EMU, /* emul reg group */
> diff --git a/hw/xen/xen_pt_stub.c b/hw/xen/xen_pt_stub.c
> index 2d8cac8d54..5c108446a8 100644
> --- a/hw/xen/xen_pt_stub.c
> +++ b/hw/xen/xen_pt_stub.c
> @@ -20,3 +20,7 @@ void xen_igd_gfx_pt_set(bool value, Error **errp)
> error_setg(errp, "Xen PCI passthrough support not built in");
> }
> }
> +
> +void xen_igd_reserve_slot(PCIBus *pci_bus)
> +{
> +}
> --
> 2.39.0