[Qemu-devel] [PATCH] Fix pc migration from qemu <= 1.5

[Cole Robinson <crobinso@redhat.com>]

The following commit introduced a migration incompatibility:

commit 568f0690fd9aa4d39d84b04c1a5dbb53a915c3fe
Author: David Gibson <david@gibson.dropbear.id.au>
Date:   Thu Jun 6 18:48:49 2013 +1000

    pci: Replace pci_find_domain() with more general pci_root_bus_path()

The issue is that i440fx savevm idstr went from 0000:00:00.0/I440FX to
0000:00.0/I440FX. Unfortunately we are stuck with the breakage for
1.6 machine types.

Add a compat property to maintain the busted idstr for the 1.6 machine
types, but revert to the old style format for 1.7+, and <= 1.5.

Tested with migration from qemu 1.5, qemu 1.6, and qemu.git.

Signed-off-by: Cole Robinson <crobinso@redhat.com>
---
 hw/i386/pc_piix.c         |  4 ++++
 hw/i386/pc_q35.c          |  4 ++++
 hw/pci-host/piix.c        |  9 ++++++++-
 hw/pci-host/q35.c         | 10 ++++++++--
 include/hw/i386/pc.h      | 28 ++++++++++++++++++++++++++++
 include/hw/pci-host/q35.h |  1 +
 6 files changed, 53 insertions(+), 3 deletions(-)

diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index c6042c7..90f1ea4 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -346,6 +346,10 @@ static QEMUMachine pc_i440fx_machine_v1_7 = {
     .alias = "pc",
     .init = pc_init_pci,
     .is_default = 1,
+    .compat_props = (GlobalProperty[]) {
+        PC_COMPAT_1_7,
+        { /* end of list */ }
+    },
 };
 
 #define PC_I440FX_1_6_MACHINE_OPTIONS PC_I440FX_MACHINE_OPTIONS
diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
index ca84e1c..569f946 100644
--- a/hw/i386/pc_q35.c
+++ b/hw/i386/pc_q35.c
@@ -270,6 +270,10 @@ static QEMUMachine pc_q35_machine_v1_7 = {
     .name = "pc-q35-1.7",
     .alias = "q35",
     .init = pc_q35_init,
+    .compat_props = (GlobalProperty[]) {
+        PC_COMPAT_1_7,
+        { /* end of list */ }
+    },
 };
 
 #define PC_Q35_1_6_MACHINE_OPTIONS PC_Q35_MACHINE_OPTIONS
diff --git a/hw/pci-host/piix.c b/hw/pci-host/piix.c
index c041149..9dafe80 100644
--- a/hw/pci-host/piix.c
+++ b/hw/pci-host/piix.c
@@ -48,6 +48,7 @@ typedef struct I440FXState {
     PCIHostState parent_obj;
     PcPciInfo pci_info;
     uint64_t pci_hole64_size;
+    uint32_t short_root_bus;
 } I440FXState;
 
 #define PIIX_NUM_PIC_IRQS       16      /* i8259 * 2 */
@@ -712,13 +713,19 @@ static const TypeInfo i440fx_info = {
 static const char *i440fx_pcihost_root_bus_path(PCIHostState *host_bridge,
                                                 PCIBus *rootbus)
 {
+    I440FXState *s = I440FX_PCI_HOST_BRIDGE(host_bridge);
+
     /* For backwards compat with old device paths */
-    return "0000";
+    if (s->short_root_bus) {
+        return "0000";
+    }
+    return "0000:00";
 }
 
 static Property i440fx_props[] = {
     DEFINE_PROP_SIZE(PCI_HOST_PROP_PCI_HOLE64_SIZE, I440FXState,
                      pci_hole64_size, DEFAULT_PCI_HOLE64_SIZE),
+    DEFINE_PROP_UINT32("short_root_bus", I440FXState, short_root_bus, 0),
     DEFINE_PROP_END_OF_LIST(),
 };
 
diff --git a/hw/pci-host/q35.c b/hw/pci-host/q35.c
index ad703a4..cb3abfd 100644
--- a/hw/pci-host/q35.c
+++ b/hw/pci-host/q35.c
@@ -61,8 +61,13 @@ static void q35_host_realize(DeviceState *dev, Error **errp)
 static const char *q35_host_root_bus_path(PCIHostState *host_bridge,
                                           PCIBus *rootbus)
 {
-    /* For backwards compat with old device paths */
-    return "0000";
+    Q35PCIHost *s = Q35_HOST_DEVICE(host_bridge);
+
+     /* For backwards compat with old device paths */
+    if (s->mch.short_root_bus) {
+        return "0000";
+    }
+    return "0000:00";
 }
 
 static void q35_host_get_pci_hole_start(Object *obj, Visitor *v,
@@ -114,6 +119,7 @@ static Property mch_props[] = {
                         MCH_HOST_BRIDGE_PCIEXBAR_DEFAULT),
     DEFINE_PROP_SIZE(PCI_HOST_PROP_PCI_HOLE64_SIZE, Q35PCIHost,
                      mch.pci_hole64_size, DEFAULT_PCI_HOLE64_SIZE),
+    DEFINE_PROP_UINT32("short_root_bus", Q35PCIHost, mch.short_root_bus, 0),
     DEFINE_PROP_END_OF_LIST(),
 };
 
diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
index 9b2ddc4..f9266f0 100644
--- a/include/hw/i386/pc.h
+++ b/include/hw/i386/pc.h
@@ -225,11 +225,31 @@ void pvpanic_init(ISABus *bus);
 
 int e820_add_entry(uint64_t, uint64_t, uint32_t);
 
+#define PC_COMPAT_1_7 \
+        {\
+            .driver   = "i440FX-pcihost",\
+            .property = "short_root_bus",\
+            .value    = stringify(0),\
+        },{\
+            .driver   = "mch",\
+            .property = "short_root_bus",\
+            .value    = stringify(0),\
+        }
+
 #define PC_COMPAT_1_6 \
+        PC_COMPAT_1_7, \
         {\
             .driver   = "e1000",\
             .property = "mitigation",\
             .value    = "off",\
+        },{\
+            .driver   = "i440FX-pcihost",\
+            .property = "short_root_bus",\
+            .value    = stringify(1),\
+        },{\
+            .driver   = "mch",\
+            .property = "short_root_bus",\
+            .value    = stringify(1),\
         }
 
 #define PC_COMPAT_1_5 \
@@ -266,6 +286,14 @@ int e820_add_entry(uint64_t, uint64_t, uint32_t);
             .driver = TYPE_X86_CPU,\
             .property = "pmu",\
             .value = "on",\
+        },{\
+            .driver   = "i440FX-pcihost",\
+            .property = "short_root_bus",\
+            .value    = stringify(0),\
+        },{\
+            .driver   = "mch",\
+            .property = "short_root_bus",\
+            .value    = stringify(0),\
         }
 
 #define PC_COMPAT_1_4 \
diff --git a/include/hw/pci-host/q35.h b/include/hw/pci-host/q35.h
index 56de92e..c8362b9 100644
--- a/include/hw/pci-host/q35.h
+++ b/include/hw/pci-host/q35.h
@@ -61,6 +61,7 @@ typedef struct MCHPCIState {
     ram_addr_t above_4g_mem_size;
     uint64_t pci_hole64_size;
     PcGuestInfo *guest_info;
+    uint32_t short_root_bus;
 } MCHPCIState;
 
 typedef struct Q35PCIHost {
-- 
1.8.3.1