Re: [Qemu-devel] [PATCH 2/6] exec.c: remove an unnecessary assert on PHYS_MAP_NODE_NIL in phys_map_node_alloc()

[Paolo Bonzini]

On 12/09/19 04:51, Wei Yang wrote:
> On Fri, Aug 23, 2019 at 09:07:50AM +0800, Wei Yang wrote:
>> On Thu, Aug 22, 2019 at 12:24:32PM +0200, Paolo Bonzini wrote:
>>> On 21/03/19 09:25, Wei Yang wrote:
>>>> PHYS_MAP_NODE_NIL is assigned to PhysPageEntry.ptr in case this is not a
>>>> leaf entry, while map->nodes_nb range in [0, nodes_nb_alloc).
>>>>
>>>> Seems we are asserting on two different things, just remove it.
>>>
>>> The assertion checks that this "if" is not entered incorrectly:
>>>
>>>    if (lp->skip && lp->ptr == PHYS_MAP_NODE_NIL) {
>>>        lp->ptr = phys_map_node_alloc(map, level == 0);
>>>    }
>>>
>>
>> Hmm... I may not get your point.
>>
>> phys_map_node_alloc() will get an available PhysPageEntry and return its
>> index, which will be assigned to its parent's ptr.
>>
>> The "if" checks on the parent's ptr, while the assertion asserts the index 
>> for
>> the new child. I may miss something?
>>
> 
> Hi, Paolo,
> 
> Do I miss something?

Sorry, I was on vacation.  phys_page_set_level can be called multiple
times, with the same lp.  The assertion checks that only the first call
will reach phys_map_node_alloc.

Paolo