Re: [PATCH v8 14/15] xen: make grant table limits boot parameters dom0 only

[Juergen Gross <jgross@suse.com>]

On 20/09/17 17:36, Jan Beulich wrote:
>>>> On 20.09.17 at 14:48, <jgross@suse.com> wrote:
>> On 20/09/17 14:07, Jan Beulich wrote:
>>>>>> On 20.09.17 at 08:34, <jgross@suse.com> wrote:
>>>> @@ -3469,14 +3460,17 @@ grant_table_create(
>>>>      /* Simple stuff. */
>>>>      percpu_rwlock_resource_init(&t->lock, grant_rwlock);
>>>>      spin_lock_init(&t->maptrack_lock);
>>>> -    t->max_grant_frames = max_grant_frames;
>>>> -    t->max_maptrack_frames = max_maptrack_frames;
>>>>  
>>>>      /* Okay, install the structure. */
>>>>      d->grant_table = t;
>>>>  
>>>>      if ( d->domain_id == 0 )
>>>> +    {
>>>> +        t->max_grant_frames = max_grant_frames ? : DEFAULT_MAX_NR_GRANT_FRAMES;
>>>> +        t->max_maptrack_frames =
>>>> +                           max_maptrack_frames ? : DEFAULT_MAX_MAPTRACK_FRAMES;
>>>>          return grant_table_init(t);
>>>> +    }
>>>
>>> The use here makes it that in effect the two variables could then
>>> become __initdata. Maybe their definition should then even move
>>> here (if the other proposal would be discarded).
>>
>> Is it possible in the hypervisor to access __initdata variables from non
>> __init functions? In the Linux kernel this is forbidden.
> 
> In Xen this is possible, and there are examples. Iirc in Linux this
> breaking the build is also just optional.

Yes, there you have the __ref annotation for __init stuff accessible
from non-__init areas.

IMHO it would be better to add:

static int __init grant_table_init_dom0()

hiding the two variables. This makes it more obvious that path is taken
only at boot time.


Juergen

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