Re: [Xen-devel] [PATCH] delte PAGE_ORDER_1G in pod

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 26/04/16 11:49, Zhang, Chunyu wrote:
> 
>> On 26/04/16 08:27, zhangcy wrote:
>>> PoD does not have cache list for 1GB pages.
>>>
>>> Signed-off-by: zhangcy <zhangcy@xxxxxxxxxxxxxx>
>>
>> Thanks for the patch.  FYI we normally tag the area in the title in a
>> structured way; I probably would have used something like the following:
>>
>> xen/pod: Remove code handling PAGE_ORDER_1G from p2m_pod_cache_add
> got it, thanks.
>>
>> But with regards to the patch itself: The question isn't whether we have
>> a cache list for 1G pages; the question is whether p2m_pod_cache_add()
>> will ever be called with order == PAGE_ORDER_1G.
>>
>> Taking a quick glance around, it looks like in theory if a guest called
>> decrease_reservation with order == PAGE_ORDER_1G, you could conceivably
>> get to p2m_pod_cache_add() with order == PAGE_ORDER_1G.
> i just think like this:
> 
> p2m_pod_decrease_reservation 
>   - if ( steal_for_cache && p2m_is_ram(t) )
>      - p2m_pod_cache_add(p2m, page, cur_order)
> i think p2m_is_ram(t) , ram also from pod cache,

No, that's memory from the guest's p2m table.  The p2m table can have 1G
entries.

 -George


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