Re: [PATCH v6 7/9] xen/arm: create shared memory nodes in guest device tree

[Julien Grall <julien@xxxxxxx>]

Hi Penny,

On 21/07/2022 14:21, Penny Zheng wrote:
> +#ifdef CONFIG_STATIC_SHM
> +static int __init make_shm_memory_node(const struct domain *d,
> +                                       void *fdt,
> +                                       int addrcells, int sizecells,
> +                                       const struct meminfo *mem)
> +{
> +    unsigned int i = 0;
> +    int res = 0;
> +
> +    if ( mem->nr_banks == 0 )
> +        return -ENOENT;
> +
> +    /*
> +     * For each shared memory region, a range is exposed under
> +     * the /reserved-memory node as a child node. Each range sub-node is
> +     * named xen-shmem@<address>.
> +     */
> +    dt_dprintk("Create xen-shmem node\n");
> +
> +    for ( ; i < mem->nr_banks; i++ )
> +    {
> +        uint64_t start = mem->bank[i].start;
> +        uint64_t size = mem->bank[i].size;
> +        /* Placeholder for xen-shmem@ + a 64-bit number + \0 */
> +        char buf[27];
> +        const char compat[] = "xen,shared-memory-v1";
> +        __be32 reg[addrcells + sizecells];
This doesn't build for me:

arch/arm/domain_build.c: In function ‘make_shm_memory_node’:
arch/arm/domain_build.c:1380:9: error: ISO C90 forbids variable length 
array ‘reg’ [-Werror=vla]
         __be32 reg[addrcells + sizecells];
         ^~~~~~

I haven't yet review the patch. But I think we would want to dynamically 
allocate 'reg' like we do in other places unless it is possible to know 
the maximum size of the array.
Cheers,

--
Julien Grall