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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 The only available workarounds are not good: Configure Xen HVM guests to use the old and no longer maintained Qemu traditional device model available from xenbits.xen.org which does reserve slot 2 for the Intel IGD or use the "pc" machine type instead of the "xenfv" machine type and add the xen platform device at slot 3 using a command line option instead of patching qemu to fix the "xenfv" machine type directly. The second workaround causes some degredation in startup performance such as a longer boot time and reduced resolution of the grub menu that is displayed on the monitor. This patch avoids that reduced startup performance when using the Qemu upstream device model for Xen HVM guests configured with the igd-passthru=on option. 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 Michael Tsirkin: * Introduce XEN_PCI_IGD_DOMAIN, XEN_PCI_IGD_BUS, XEN_PCI_IGD_DEV, and XEN_PCI_IGD_FN - use them to compute the value of XEN_PCI_IGD_SLOT_MASK 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. 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> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org> Message-Id: <b1b4a21fe9a600b1322742dda55a40e9961daa57.1674346505.git.brchuckz@aol.com> Signed-off-by: Anthony PERARD <anthony.perard@citrix.com> (cherry picked from commit 4f67543bb8c5b031c2ad3785c1a2f3c255d72b25) Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
27 lines
519 B
C
27 lines
519 B
C
/*
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* Copyright (C) 2020 Citrix Systems UK Ltd.
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or later.
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* See the COPYING file in the top-level directory.
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*/
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#include "qemu/osdep.h"
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#include "hw/xen/xen_pt.h"
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#include "qapi/error.h"
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bool xen_igd_gfx_pt_enabled(void)
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{
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return false;
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}
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void xen_igd_gfx_pt_set(bool value, Error **errp)
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{
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if (value) {
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error_setg(errp, "Xen PCI passthrough support not built in");
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}
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}
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void xen_igd_reserve_slot(PCIBus *pci_bus)
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{
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}
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