[PATCH v3 2/2] hw/pci-host: save/restore pci host config register for old ones

[Hogan Wang]

The i440fx and q35 machines integrate i440FX or MCH PCI device by default.
Refer to i440FX and ICH9-LPC spcifications, there are some reserved
configuration registers can used to save/restore PCIHostState.config_reg.
It's nasty but friendly to old ones.

Signed-off-by: Hogan Wang <hogan.wang@huawei.com>
---
 hw/pci-host/i440fx.c | 31 +++++++++++++++++++++++++++++++
 hw/pci-host/q35.c    | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+)

diff --git a/hw/pci-host/i440fx.c b/hw/pci-host/i440fx.c
index c662903dbb..9e2cfdb052 100644
--- a/hw/pci-host/i440fx.c
+++ b/hw/pci-host/i440fx.c
@@ -65,6 +65,14 @@ typedef struct I440FXState {
  */
 #define I440FX_COREBOOT_RAM_SIZE 0x57
 
+/* Older I440FX machines (5.0 and older) not support i440FX-pcihost state
+ * migration, use some reserved INTEL 82441 configuration registers to
+ * save/restore i440FX-pcihost config register. Refer to [INTEL 440FX PCISET
+ * 82441FX PCI AND MEMORY CONTROLLER (PMC) AND 82442FX DATA BUS ACCELERATOR
+ * (DBX) Table 1. PMC Configuration Space]
+ */
+#define I440FX_PCI_HOST_CONFIG_REG 0x94
+
 static void i440fx_update_memory_mappings(PCII440FXState *d)
 {
     int i;
@@ -99,8 +107,30 @@ static void i440fx_write_config(PCIDevice *dev,
 static int i440fx_post_load(void *opaque, int version_id)
 {
     PCII440FXState *d = opaque;
+    uint8_t *config;
+    I440FXState *s = OBJECT_CHECK(I440FXState,
+                                  object_resolve_path("/machine/i440fx", NULL),
+                                  TYPE_PCI_HOST_BRIDGE);
 
     i440fx_update_memory_mappings(d);
+
+    if (!s->migration_enabled) {
+        config = &d->parent_obj.config[I440FX_PCI_HOST_CONFIG_REG];
+        s->parent_obj.config_reg = pci_get_long(config);
+    }
+    return 0;
+}
+
+static int i440fx_pre_save(void *opaque)
+{
+    PCIDevice *d = opaque;
+    I440FXState *s = OBJECT_CHECK(I440FXState,
+                                  object_resolve_path("/machine/i440fx", NULL),
+                                  TYPE_PCI_HOST_BRIDGE);
+    if (!s->migration_enabled) {
+        pci_set_long(&d->config[I440FX_PCI_HOST_CONFIG_REG],
+                     s->parent_obj.config_reg);
+    }
     return 0;
 }
 
@@ -108,6 +138,7 @@ static const VMStateDescription vmstate_i440fx = {
     .name = "I440FX",
     .version_id = 3,
     .minimum_version_id = 3,
+    .pre_save = i440fx_pre_save,
     .post_load = i440fx_post_load,
     .fields = (VMStateField[]) {
         VMSTATE_PCI_DEVICE(parent_obj, PCII440FXState),
diff --git a/hw/pci-host/q35.c b/hw/pci-host/q35.c
index bb41665da4..67e08dedc5 100644
--- a/hw/pci-host/q35.c
+++ b/hw/pci-host/q35.c
@@ -43,6 +43,15 @@
 
 #define Q35_PCI_HOST_HOLE64_SIZE_DEFAULT (1ULL << 35)
 
+/* Older Q35 machines (5.0 and older) not support q35-pcihost state
+ * migration, use some reserved INTEL MCH configuration registers to
+ * save/restore q35-pcihost config register. Refer to [Intel 3 Series
+ * Chipset Family Datasheet Table 5-1. DRAM Controller Register Address
+ * Map (D0:F0)]
+ */
+#define Q35_PCI_HOST_CONFIG_REG 0x70
+
+
 static void q35_host_realize(DeviceState *dev, Error **errp)
 {
     PCIHostState *pci = PCI_HOST_BRIDGE(dev);
@@ -532,7 +541,34 @@ static void mch_update(MCHPCIState *mch)
 static int mch_post_load(void *opaque, int version_id)
 {
     MCHPCIState *mch = opaque;
+    uint8_t *config;
+    Q35PCIHost *s = OBJECT_CHECK(Q35PCIHost,
+                                 object_resolve_path("/machine/q35", NULL),
+                                 TYPE_PCI_HOST_BRIDGE);
+    PCIHostState *pci = PCI_HOST_BRIDGE(s);
+
     mch_update(mch);
+    if (!s->migration_enabled) {
+        config = &mch->parent_obj.config[Q35_PCI_HOST_CONFIG_REG];
+        pci->config_reg = pci_get_long(config);
+    }
+
+    return 0;
+}
+
+static int mch_pre_save(void *opaque)
+{
+    MCHPCIState *mch = opaque;
+    uint8_t *config;
+    Q35PCIHost *s = OBJECT_CHECK(Q35PCIHost,
+                                 object_resolve_path("/machine/q35", NULL),
+                                 TYPE_PCI_HOST_BRIDGE);
+    PCIHostState *pci = PCI_HOST_BRIDGE(s);
+
+    if (!s->migration_enabled) {
+        config = &mch->parent_obj.config[Q35_PCI_HOST_CONFIG_REG];
+        pci_set_long(config, pci->config_reg);
+    }
     return 0;
 }
 
@@ -540,6 +576,7 @@ static const VMStateDescription vmstate_mch = {
     .name = "mch",
     .version_id = 1,
     .minimum_version_id = 1,
+    .pre_save = mch_pre_save,
     .post_load = mch_post_load,
     .fields = (VMStateField[]) {
         VMSTATE_PCI_DEVICE(parent_obj, MCHPCIState),
-- 
2.27.0