On Tue, 2015-09-15 at 18:30 -0700, Mitchel Humpherys wrote:

> Any overlap in the reserved memory regions (those specified in the
> reserved-memory DT node) is a bug.  These bugs might go undetected as
> long as the contested region isn't used simultaneously by multiple
> software agents, which makes such bugs hard to debug.  Fix this by
> printing a scary warning during boot if overlap is detected.
> 
> diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
> index 726ebe792813..62f467b8ccae 100644
> --- a/drivers/of/of_reserved_mem.c
> +++ b/drivers/of/of_reserved_mem.c
> @@ -197,12 +198,52 @@ static int __init __reserved_mem_init_node(struct 
> reserved_mem *rmem)
>       return -ENOENT;
>  }
>  
> +static int __init __rmem_cmp(const void *a, const void *b)
> +{
> +     const struct reserved_mem *ra = a, *rb = b;
> +
> +     return ra->base - rb->base;
> +}
> +
> +static void __init __rmem_check_for_overlap(void)
> +{
> +     int i;
> +
> +     if (reserved_mem_count < 2)
> +             return;
> +
> +     sort(reserved_mem, reserved_mem_count, sizeof(reserved_mem[0]),
> +          __rmem_cmp, NULL);
> +     for (i = 0; i < reserved_mem_count - 1; i++) {
> +             struct reserved_mem *this, *next;
> +
> +             this = &reserved_mem[i];
> +             next = &reserved_mem[i + 1];
> +             if (!(this->base && next->base))
> +                     continue;
> +             if (this->base + this->size > next->base) {
> +                     phys_addr_t this_end, next_end;
> +
> +                     this_end = this->base + this->size;
> +                     next_end = next->base + next->size;
> +                     WARN(1,
> +                          "Reserved memory: OVERLAP DETECTED!\n%s (%pa--%pa) 
> overlaps with %s (%pa--%pa)\n",
> +                          this->name, &this->base, &this_end,
> +                          next->name, &next->base, &next_end);

This is blowing up on some powerpc machines.

It's too early in boot to call WARN() on these systems.

Can we turn it into a pr_err() for now?

I'll send a patch?

cheers

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