Re: [XEN][PATCH v9 01/19] common/device_tree: handle memory allocation failure in __unflatten_device_tree()

[Julien Grall <julien@xxxxxxx>]

Hi Vikram,

On 19/08/2023 01:28, Vikram Garhwal wrote:
> Change __unflatten_device_tree() return type to integer so it can propagate
> memory allocation failure. Add panic() in dt_unflatten_host_device_tree() for
> memory allocation failure during boot.
>
> Fixes: fb97eb614acf ("xen/arm: Create a hierarchical device tree")
> Signed-off-by: Vikram Garhwal <vikram.garhwal@xxxxxxx>
> Reviewed-by: Henry Wang <Henry.Wang@xxxxxxx>
> Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>
> Acked-by: Julien Grall <jgrall@xxxxxxxxxx>
> ---
>   xen/common/device_tree.c | 14 +++++++++++---
>   1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c
> index 0522fdf976..c91d54c493 100644
> --- a/xen/common/device_tree.c
> +++ b/xen/common/device_tree.c
> @@ -2092,8 +2092,8 @@ static unsigned long __init unflatten_dt_node(const void 
> *fdt,
>    * @fdt: The fdt to expand
>    * @mynodes: The device_node tree created by the call
>    */
While looking at patch #4, I noticed that the comment wasn't updated to 
mention the meaning of the return value. Can this be done?
If you propose a new comment on the ML, I can update it while committing 
patch. IOW no need to resend a new version for this patch.
> -static void __init __unflatten_device_tree(const void *fdt,
> -                                           struct dt_device_node **mynodes)
> +static int __init __unflatten_device_tree(const void *fdt,
> +                                          struct dt_device_node **mynodes)
>   {
>       unsigned long start, mem, size;
>       struct dt_device_node **allnextp = mynodes;
> @@ -2114,6 +2114,8 @@ static void __init __unflatten_device_tree(const void 
> *fdt,
>   
>       /* Allocate memory for the expanded device tree */
>       mem = (unsigned long)_xmalloc (size + 4, __alignof__(struct 
> dt_device_node));
> +    if ( !mem )
> +        return -ENOMEM;
>   
>       ((__be32 *)mem)[size / 4] = cpu_to_be32(0xdeadbeefU);
>   
> @@ -2131,6 +2133,8 @@ static void __init __unflatten_device_tree(const void *fdt,
>       *allnextp = NULL;
>   
>       dt_dprintk(" <- unflatten_device_tree()\n");
> +
> +    return 0;
>   }
>   
>   static void dt_alias_add(struct dt_alias_prop *ap,
> @@ -2215,7 +2219,11 @@ dt_find_interrupt_controller(const struct 
> dt_device_match *matches)
>   
>   void __init dt_unflatten_host_device_tree(void)
>   {
> -    __unflatten_device_tree(device_tree_flattened, &dt_host);
> +    int error = __unflatten_device_tree(device_tree_flattened, &dt_host);
> +
> +    if ( error )
> +        panic("__unflatten_device_tree failed with error %d\n", error);
> +
>       dt_alias_scan();
>   }
>   
Cheers,

--
Julien Grall