Re: [Xen-devel] [PATCH v8 11/15] xen: delay allocation of grant table sub structures

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 20.09.17 at 11:44, <jgross@xxxxxxxx> wrote:
> On 20/09/17 11:22, Jan Beulich wrote:
>>>>> On 20.09.17 at 08:34, <jgross@xxxxxxxx> wrote:
>>> @@ -3381,75 +3425,21 @@ grant_table_create(
>>>      struct domain *d)
>>>  {
>>>      struct grant_table *t;
>>> -    unsigned int i, j;
>>>  
>>>      if ( (t = xzalloc(struct grant_table)) == NULL )
>>> -        goto no_mem_0;
>>> +        return -ENOMEM;
>>>  
>>>      /* Simple stuff. */
>>>      percpu_rwlock_resource_init(&t->lock, grant_rwlock);
>>>      spin_lock_init(&t->maptrack_lock);
>>> -    t->nr_grant_frames = INITIAL_NR_GRANT_FRAMES;
>>> -
>>> -    /* Active grant table. */
>>> -    if ( (t->active = xzalloc_array(struct active_grant_entry *,
>>> -                                    max_nr_active_grant_frames)) == NULL )
>>> -        goto no_mem_1;
>>> -    for ( i = 0;
>>> -          i < num_act_frames_from_sha_frames(INITIAL_NR_GRANT_FRAMES); i++ 
>>> )
>>> -    {
>>> -        if ( (t->active[i] = alloc_xenheap_page()) == NULL )
>>> -            goto no_mem_2;
>>> -        clear_page(t->active[i]);
>>> -        for ( j = 0; j < ACGNT_PER_PAGE; j++ )
>>> -            spin_lock_init(&t->active[i][j].lock);
>>> -    }
>>> -
>>> -    /* Tracking of mapped foreign frames table */
>>> -    t->maptrack = vzalloc(max_maptrack_frames * sizeof(*t->maptrack));
>>> -    if ( t->maptrack == NULL )
>>> -        goto no_mem_2;
>>> -
>>> -    /* Shared grant table. */
>>> -    if ( (t->shared_raw = xzalloc_array(void *, max_grant_frames)) == NULL 
>>> )
>>> -        goto no_mem_3;
>>> -    for ( i = 0; i < INITIAL_NR_GRANT_FRAMES; i++ )
>>> -    {
>>> -        if ( (t->shared_raw[i] = alloc_xenheap_page()) == NULL )
>>> -            goto no_mem_4;
>>> -        clear_page(t->shared_raw[i]);
>>> -    }
>>> -
>>> -    /* Status pages for grant table - for version 2 */
>>> -    t->status = xzalloc_array(grant_status_t *,
>>> -                              grant_to_status_frames(max_grant_frames));
>>> -    if ( t->status == NULL )
>>> -        goto no_mem_4;
>>> -
>>> -    for ( i = 0; i < INITIAL_NR_GRANT_FRAMES; i++ )
>>> -        gnttab_create_shared_page(d, t, i);
>>> -
>>> -    t->nr_status_frames = 0;
>>>  
>>>      /* Okay, install the structure. */
>>>      d->grant_table = t;
>>> -    return 0;
>>>  
>>> - no_mem_4:
>>> -    for ( i = 0; i < INITIAL_NR_GRANT_FRAMES; i++ )
>>> -        free_xenheap_page(t->shared_raw[i]);
>>> -    xfree(t->shared_raw);
>>> - no_mem_3:
>>> -    vfree(t->maptrack);
>>> - no_mem_2:
>>> -    for ( i = 0;
>>> -          i < num_act_frames_from_sha_frames(INITIAL_NR_GRANT_FRAMES); i++ 
>>> )
>>> -        free_xenheap_page(t->active[i]);
>>> -    xfree(t->active);
>>> - no_mem_1:
>>> -    xfree(t);
>>> - no_mem_0:
>>> -    return -ENOMEM;
>>> +    if ( d->domain_id == 0 )
>>> +        return grant_table_init(t);
>>> +
>>> +    return 0;
>>>  }
>>>  
>>>  void
>>> @@ -3651,8 +3641,9 @@ int grant_table_set_limits(struct domain *d, unsigned 
>>> int grant_frames,
>>>  
>>>      grant_write_lock(gt);
>>>  
>>> -    ret = 0;
>>> -    /* Set limits, alloc needed arrays. */
>>> +    /* Set limits. */
>>> +    if ( !gt->active )
>>> +        ret = grant_table_init(gt);
>>>  
>>>      grant_write_unlock(gt);
>> 
>> These changes don't leave the domains in a state similar to that
>> before the change - I'm missing calls to gnttab_grow_table() to
>> establish the minimal sizes. Aiui so far there has been no
>> requirement for a domain to invoke GNTTABOP_setup_table if it
>> is happy with v1 and the minimum size.
> 
> So you don't like gnttab_grow_table() being called when the guest tries
> to map the grant frames in this case?

I don't like it being called _only_ in that case.

> I can add the call of gnttab_grow_table() to grant_table_set_limits() in
> case you like that better.

And to grant_table_create() for the Dom0 case.

Jan


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