[Qemu-devel] [PULL 01/18] PPC: E500: Generate device tree on reset

[Alexander Graf <agraf@suse.de>]

Today we generate the device tree once on machine initialization and then
store the finalized blob in memory to reload it on reset.

This is bad for 2 reasons. First we potentially waste a bunch of RAM for no
good reason, as we have all information required to regenerate the device
tree available anyways.

The second reason is even more important. On machine init when we generate
the device tree for the first time, we don't have all of the devices fully
initialized yet. But the device tree needs to potentially walk devices to
put information about them into the device tree.

Move the generation into a reset function. That way we just generate it new
every time we reset, solving both of the above issues.

Signed-off-by: Alexander Graf <agraf@suse.de>
---
 hw/ppc/e500.c | 52 +++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 43 insertions(+), 9 deletions(-)

diff --git a/hw/ppc/e500.c b/hw/ppc/e500.c
index e79612b..9059ff9 100644
--- a/hw/ppc/e500.c
+++ b/hw/ppc/e500.c
@@ -123,13 +123,14 @@ static void dt_serial_create(void *fdt, unsigned long long offset,
     }
 }
 
-static int ppce500_load_device_tree(CPUPPCState *env,
-                                    QEMUMachineInitArgs *args,
+static int ppce500_load_device_tree(QEMUMachineInitArgs *args,
                                     PPCE500Params *params,
                                     hwaddr addr,
                                     hwaddr initrd_base,
-                                    hwaddr initrd_size)
+                                    hwaddr initrd_size,
+                                    bool dry_run)
 {
+    CPUPPCState *env = first_cpu->env_ptr;
     int ret = -1;
     uint64_t mem_reg_property[] = { 0, cpu_to_be64(args->ram_size) };
     int fdt_size;
@@ -369,12 +370,10 @@ static int ppce500_load_device_tree(CPUPPCState *env,
     }
 
 done:
-    qemu_devtree_dumpdtb(fdt, fdt_size);
-    ret = rom_add_blob_fixed(BINARY_DEVICE_TREE_FILE, fdt, fdt_size, addr);
-    if (ret < 0) {
-        goto out;
+    if (!dry_run) {
+        qemu_devtree_dumpdtb(fdt, fdt_size);
+        cpu_physical_memory_write(addr, fdt, fdt_size);
     }
-    g_free(fdt);
     ret = fdt_size;
 
 out:
@@ -383,6 +382,41 @@ out:
     return ret;
 }
 
+typedef struct DeviceTreeParams {
+    QEMUMachineInitArgs args;
+    PPCE500Params params;
+    hwaddr addr;
+    hwaddr initrd_base;
+    hwaddr initrd_size;
+} DeviceTreeParams;
+
+static void ppce500_reset_device_tree(void *opaque)
+{
+    DeviceTreeParams *p = opaque;
+    ppce500_load_device_tree(&p->args, &p->params, p->addr, p->initrd_base,
+                             p->initrd_size, false);
+}
+
+static int ppce500_prep_device_tree(QEMUMachineInitArgs *args,
+                                    PPCE500Params *params,
+                                    hwaddr addr,
+                                    hwaddr initrd_base,
+                                    hwaddr initrd_size)
+{
+    DeviceTreeParams *p = g_new(DeviceTreeParams, 1);
+    p->args = *args;
+    p->params = *params;
+    p->addr = addr;
+    p->initrd_base = initrd_base;
+    p->initrd_size = initrd_size;
+
+    qemu_register_reset(ppce500_reset_device_tree, p);
+
+    /* Issue the device tree loader once, so that we get the size of the blob */
+    return ppce500_load_device_tree(args, params, addr, initrd_base,
+                                    initrd_size, true);
+}
+
 /* Create -kernel TLB entries for BookE.  */
 static inline hwaddr booke206_page_size_to_tlb(uint64_t size)
 {
@@ -746,7 +780,7 @@ void ppce500_init(QEMUMachineInitArgs *args, PPCE500Params *params)
         struct boot_info *boot_info;
         int dt_size;
 
-        dt_size = ppce500_load_device_tree(env, args, params, dt_base,
+        dt_size = ppce500_prep_device_tree(args, params, dt_base,
                                            initrd_base, initrd_size);
         if (dt_size < 0) {
             fprintf(stderr, "couldn't load device tree\n");
-- 
1.8.1.4