i386/acpi: restore device paths for pre-5.1 vms

After fixing the _UID value for the primary PCI root bridge in
af1b80a it was discovered that this change updates Windows
configuration in an incompatible way causing network configuration
failure unless DHCP is used. More details provided on the list:

https://lists.gnu.org/archive/html/qemu-devel/2021-02/msg08484.html

This change reverts the _UID update from 1 to 0 for q35 and i440fx
VMs before version 5.2 to maintain the original behaviour when
upgrading.

Cc: qemu-stable@nongnu.org
Cc: qemu-devel@nongnu.org
Reported-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
Suggested-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Vitaly Cheptsov <cheptsov@ispras.ru>
Message-Id: <20210301195919.9333-1-cheptsov@ispras.ru>
Tested-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Fixes: af1b80a ("i386/acpi: fix inconsistent QEMU/OVMF device paths")

hw/i386/acpi-build.c

@@ -1277,7 +1277,7 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
         dev = aml_device("PCI0");
         aml_append(dev, aml_name_decl("_HID", aml_eisaid("PNP0A03")));
         aml_append(dev, aml_name_decl("_ADR", aml_int(0)));
-        aml_append(dev, aml_name_decl("_UID", aml_int(0)));
+        aml_append(dev, aml_name_decl("_UID", aml_int(pcmc->pci_root_uid)));
         aml_append(sb_scope, dev);
         aml_append(dsdt, sb_scope);
 
@@ -1296,7 +1296,7 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
         aml_append(dev, aml_name_decl("_HID", aml_eisaid("PNP0A08")));
         aml_append(dev, aml_name_decl("_CID", aml_eisaid("PNP0A03")));
         aml_append(dev, aml_name_decl("_ADR", aml_int(0)));
-        aml_append(dev, aml_name_decl("_UID", aml_int(0)));
+        aml_append(dev, aml_name_decl("_UID", aml_int(pcmc->pci_root_uid)));
         aml_append(dev, build_q35_osc_method());
         aml_append(sb_scope, dev);
         if (mcfg_valid) {

hw/i386/pc_piix.c

@@ -405,6 +405,7 @@ static void pc_i440fx_machine_options(MachineClass *m)
 {
     PCMachineClass *pcmc = PC_MACHINE_CLASS(m);
     pcmc->default_nic_model = "e1000";
+    pcmc->pci_root_uid = 0;
 
     m->family = "pc_piix";
     m->desc = "Standard PC (i440FX + PIIX, 1996)";
@@ -448,6 +449,7 @@ static void pc_i440fx_5_1_machine_options(MachineClass *m)
     compat_props_add(m->compat_props, hw_compat_5_1, hw_compat_5_1_len);
     compat_props_add(m->compat_props, pc_compat_5_1, pc_compat_5_1_len);
     pcmc->kvmclock_create_always = false;
+    pcmc->pci_root_uid = 1;
 }
 
 DEFINE_I440FX_MACHINE(v5_1, "pc-i440fx-5.1", NULL,

hw/i386/pc_q35.c

@@ -329,6 +329,7 @@ static void pc_q35_machine_options(MachineClass *m)
 {
     PCMachineClass *pcmc = PC_MACHINE_CLASS(m);
     pcmc->default_nic_model = "e1000e";
+    pcmc->pci_root_uid = 0;
 
     m->family = "pc_q35";
     m->desc = "Standard PC (Q35 + ICH9, 2009)";
@@ -375,6 +376,7 @@ static void pc_q35_5_1_machine_options(MachineClass *m)
     compat_props_add(m->compat_props, hw_compat_5_1, hw_compat_5_1_len);
     compat_props_add(m->compat_props, pc_compat_5_1, pc_compat_5_1_len);
     pcmc->kvmclock_create_always = false;
+    pcmc->pci_root_uid = 1;
 }
 
 DEFINE_Q35_MACHINE(v5_1, "pc-q35-5.1", NULL,

include/hw/i386/pc.h

@@ -105,6 +105,7 @@ struct PCMachineClass {
     int legacy_acpi_table_size;
     unsigned acpi_data_size;
     bool do_not_add_smb_acpi;
+    int pci_root_uid;
 
     /* SMBIOS compat: */
     bool smbios_defaults;