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>

1 files changed, 23 insertions, 0 deletions

diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
index 08539a1aab..282ba93e2e 100644
--- a/hw/nvram/fw_cfg.c
+++ b/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());