Re: [PATCH] hw/riscv: Skip re-generating DT nodes for a given DTB

[Daniel Henrique Barboza]

On 2/21/23 03:12, Bin Meng wrote:

Lanuch qemu-system-riscv64 with a given dtb for 'sifive_u' and 'virt'
machines, QEMU complains:

   qemu_fdt_add_subnode: Failed to create subnode /soc: FDT_ERR_EXISTS

The whole DT generation logic should be skipped when a given DTB is
present.

Fixes: b1f19f238cae ("hw/riscv: write bootargs 'chosen' FDT after 
riscv_load_kernel()")

Thanks for cleaning my mess :)

I was wondering whether we should move the ms->dtb verification/load bits 
outside of
create_fdt(), and put it explicitly in sifive_u_machine_init() and 
virt_machine_init().
Like this:

    /* load/create device tree*/
    if (ms->dtb) {
        ms->fdt = load_device_tree(ms->dtb, &s->fdt_size);
        if (!ms->fdt) {
            error_report("load_device_tree() failed");
            exit(1);
        }
    } else {
        create_fdt(s, memmap);
    }


This looks clearer to me because create_fdt() will actually create a fdt, not 
load or create
a fdt. create_fdt() from spike works this way.

I'll leave to your discretion. The patch is already good enough as is.


Reviewed-by: Daniel Henrique Barboza <dbarb...@ventanamicro.com>

Signed-off-by: Bin Meng <bm...@tinylab.org>
---

  hw/riscv/sifive_u.c | 1 +
  hw/riscv/virt.c     | 1 +
  2 files changed, 2 insertions(+)

diff --git a/hw/riscv/sifive_u.c b/hw/riscv/sifive_u.c
index ad3bb35b34..76db5ed3dd 100644
--- a/hw/riscv/sifive_u.c
+++ b/hw/riscv/sifive_u.c
@@ -118,6 +118,7 @@ static void create_fdt(SiFiveUState *s, const MemMapEntry 
*memmap,
              error_report("load_device_tree() failed");
              exit(1);
          }
+        return;
      } else {
          fdt = ms->fdt = create_device_tree(&fdt_size);
          if (!fdt) {
diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
index 86c4adc0c9..0c7b4a1e46 100644
--- a/hw/riscv/virt.c
+++ b/hw/riscv/virt.c
@@ -1014,6 +1014,7 @@ static void create_fdt(RISCVVirtState *s, const 
MemMapEntry *memmap)
              error_report("load_device_tree() failed");
              exit(1);
          }
+        return;
      } else {
          ms->fdt = create_device_tree(&s->fdt_size);
          if (!ms->fdt) {