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

[Julien Grall <julien.grall@linaro.org>]

On 11/13/2013 01:26 PM, Jan Beulich wrote:
>>>> On 13.11.13 at 14:15, Julien Grall <julien.grall@linaro.org> 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@linaro.org>
>> CC: Keir Fraser <keir@xen.org>
>> CC: Jan Beulich <jbeulich@suse.com>
>>
>> ---
>>      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).

if ps == pe, then emfn == (smfn - 1). This will result to the number of 
pages of -1.

There is a similar check in init_xenheap_pages, it doesn't seem harmfull 
to let it here.

-- 
Julien Grall