Re: [Xen-devel] [PATCH] kexec: allow relaxed placement specification via command line

[David Vrabel <david.vrabel@xxxxxxxxxx>]

On 31/05/16 13:44, Jan Beulich wrote:
>>>> On 31.05.16 at 12:30, <david.vrabel@xxxxxxxxxx> wrote:
>> On 30/05/16 14:48, Jan Beulich wrote:
>>> --- a/xen/arch/x86/setup.c
>>> +++ b/xen/arch/x86/setup.c
>>> @@ -1044,13 +1044,19 @@ void __init noreturn __start_xen(unsigne
>>>          }
>>>  
>>>  #ifdef CONFIG_KEXEC
>>> -        /* Don't overlap with modules. */
>>> -        e = consider_modules(s, e, PAGE_ALIGN(kexec_crash_area.size),
>>> -                             mod, mbi->mods_count, -1);
>>> -        if ( !kexec_crash_area.start && (s < e) )
>>
>> I think we want a comment here.
>>
>> /*
>>  * Looking backwards from the crash area limit, find a large enough
>>  * crash area that does not overlap with modules.
>>  */
> 
> Sure, added.
> 
>>> +        while ( !kexec_crash_area.start )
>>
>> Does this mean that if an @<offset> is specified we no longer check for
>> overlapping modules?
> 
> We didn't do any more checking before. If you look at the old
> code above, we called consider_modules() only to possibly alter
> e. All the rest of the old code was similarly dependent upon
> !kexec_crash_area.start. That other case is being taken care
> of earlier anyway - see kexec_reserve_area()'s first invocation.
> 
> But yes, it looks like there's an overlap check missing there (iiuc
> relevant really only for the initrd, as that's the only thing the
> memory of which may not get copied but simply directly handed
> to Dom0).

Ok.  Any additional improvement can be done later so if you add the comment,

Reviewed-by: David Vrabel <david.vrabel@xxxxxxxxxx>

David

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