Re: [PATCH v2] ppc/pnv.c: fix "system-id" FDT when -uuid is set

[David Gibson]

On Mon, Dec 06, 2021 at 10:02:53AM -0300, Daniel Henrique Barboza wrote:
> Setting -uuid in the pnv machine does not work:
> 
> ./qemu-system-ppc64 -machine powernv8,accel=tcg  -uuid 
> 7ff61ca1-a4a0-4bc1-944c-abd114a35e80
> qemu-system-ppc64: error creating device tree: (fdt_property_string(fdt, 
> "system-id", buf)): FDT_ERR_BADSTATE
> 
> This happens because we're using "fdt_property_string" to retrieve a
> "system-id" attribute that does not exist, instead of using
> fdt_setprop_string() to create a "system-id" attribute with the uuid
> provided via command line.

Fix is correct but this description isn't really accurate.
fdt_property_string() is a "sequential write" function, only used when
you're building a new DT up from scratch, which is an entirely
different mode from read/write access to an existing tree.  Using when
the tree is in read-write state will cause an immediate BADSTATE
error; whether the property exists already or not is irrelevant.

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> 
> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
> ---
> 
> changes from v1:
> - fixed typo in commit title
> 
> 
>  hw/ppc/pnv.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/hw/ppc/pnv.c b/hw/ppc/pnv.c
> index 32ab8071a4..9e532caa9f 100644
> --- a/hw/ppc/pnv.c
> +++ b/hw/ppc/pnv.c
> @@ -552,7 +552,7 @@ static void *pnv_dt_create(MachineState *machine)
>      buf =  qemu_uuid_unparse_strdup(&qemu_uuid);
>      _FDT((fdt_setprop_string(fdt, 0, "vm,uuid", buf)));
>      if (qemu_uuid_set) {
> -        _FDT((fdt_property_string(fdt, "system-id", buf)));
> +        _FDT((fdt_setprop_string(fdt, 0, "system-id", buf)));
>      }
>      g_free(buf);
>  

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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