fw_cfg: Refactor extra pci roots addition

Extract extra pci roots addition from pc machine, which could be used by
other machines.

In order to make uefi get the extra roots, it is necessary to write extra
roots into fw_cfg. And only if the uefi knows there are extra roots,
the config spaces of devices behind the root could be obtained.

Signed-off-by: Jiahui Cen <cenjiahui@huawei.com>
Signed-off-by: Yubo Miao <miaoyubo@huawei.com>
Message-Id: <20201119014841.7298-3-cenjiahui@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/i386/pc.c

@@ -777,27 +777,11 @@ void pc_machine_done(Notifier *notifier, void *data)
     PCMachineState *pcms = container_of(notifier,
                                         PCMachineState, machine_done);
     X86MachineState *x86ms = X86_MACHINE(pcms);
-    PCIBus *bus = pcms->bus;
 
     /* set the number of CPUs */
     x86_rtc_set_cpus_count(x86ms->rtc, x86ms->boot_cpus);
 
-    if (bus) {
+    fw_cfg_add_extra_pci_roots(pcms->bus, x86ms->fw_cfg);
-        int extra_hosts = 0;
-
-        QLIST_FOREACH(bus, &bus->child, sibling) {
-            /* look for expander root buses */
-            if (pci_bus_is_root(bus)) {
-                extra_hosts++;
-            }
-        }
-        if (extra_hosts && x86ms->fw_cfg) {
-            uint64_t *val = g_malloc(sizeof(*val));
-            *val = cpu_to_le64(extra_hosts);
-            fw_cfg_add_file(x86ms->fw_cfg,
-                    "etc/extra-pci-roots", val, sizeof(*val));
-        }
-    }
 
     acpi_setup();
     if (x86ms->fw_cfg) {

hw/nvram/fw_cfg.c

@@ -40,6 +40,7 @@
 #include "qemu/cutils.h"
 #include "qapi/error.h"
 #include "hw/acpi/aml-build.h"
+#include "hw/pci/pci_bus.h"
 
 #define FW_CFG_FILE_SLOTS_DFLT 0x20
 
@@ -1061,6 +1062,28 @@ bool fw_cfg_add_from_generator(FWCfgState *s, const char *filename,
     return true;
 }
 
+void fw_cfg_add_extra_pci_roots(PCIBus *bus, FWCfgState *s)
+{
+    int extra_hosts = 0;
+
+    if (!bus) {
+        return;
+    }
+
+    QLIST_FOREACH(bus, &bus->child, sibling) {
+        /* look for expander root buses */
+        if (pci_bus_is_root(bus)) {
+            extra_hosts++;
+        }
+    }
+
+    if (extra_hosts && s) {
+        uint64_t *val = g_malloc(sizeof(*val));
+        *val = cpu_to_le64(extra_hosts);
+        fw_cfg_add_file(s, "etc/extra-pci-roots", val, sizeof(*val));
+    }
+}
+
 static void fw_cfg_machine_reset(void *opaque)
 {
     MachineClass *mc = MACHINE_GET_CLASS(qdev_get_machine());

include/hw/nvram/fw_cfg.h

@@ -308,6 +308,15 @@ void *fw_cfg_modify_file(FWCfgState *s, const char *filename, void *data,
 bool fw_cfg_add_from_generator(FWCfgState *s, const char *filename,
                                const char *gen_id, Error **errp);
 
+/**
+ * fw_cfg_add_extra_pci_roots:
+ * @bus: main pci root bus to be scanned from
+ * @s: fw_cfg device being modified
+ *
+ * Add a new fw_cfg item...
+ */
+void fw_cfg_add_extra_pci_roots(PCIBus *bus, FWCfgState *s);
+
 FWCfgState *fw_cfg_init_io_dma(uint32_t iobase, uint32_t dma_iobase,
                                 AddressSpace *dma_as);
 FWCfgState *fw_cfg_init_io(uint32_t iobase);