Re: [Xen-devel] [PATCH V2] xen: Check if the range is valid in init_domheap_pages

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 13.11.13 at 14:15, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
> On ARM, when an initrd is given to xen by U-boot, it will reserve the memory 
> in the device tree.
> In this case, when xen decides to free unused memory, dt_unreserved_regions
> will call init_domheap_pages with the start and the end of range equals. But
> the latter assumes that (start > end), if not Xen will hang because the
> number of pages is equals to (unsigned)-1.

The change is simple enough, so I don't really mind it going in, but
I wonder ...

> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> CC: Keir Fraser <keir@xxxxxxx>
> CC: Jan Beulich <jbeulich@xxxxxxxx>
> 
> ---
>     Changes in v2:
>         - Change commit title
>         - Move the check in init_domheap_pages

... who and why suggested to move it here. After all, I'm considering
it an error to call the function with non-page-aligned addresses and/
or end < start (I take it that page-aligned, but start == end is not a
problem without your change).

Jan

> --- a/xen/common/page_alloc.c
> +++ b/xen/common/page_alloc.c
> @@ -1429,6 +1429,9 @@ void init_domheap_pages(paddr_t ps, paddr_t pe)
>      smfn = round_pgup(ps) >> PAGE_SHIFT;
>      emfn = round_pgdown(pe) >> PAGE_SHIFT;
>  
> +    if ( smfn <= emfn )
> +        return;
> +
>      init_heap_pages(mfn_to_page(smfn), emfn - smfn);
>  }
>  
> -- 
> 1.8.3.1
> 
> 
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