From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jeremy Fitzhardinge <jeremy@goop.org>
Subject: Re: [PATCH] Add memory hotadd to pvops dom0
Date: Sat, 19 Dec 2009 22:40:51 -0800
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To: "Jiang, Yunhong" <yunhong.jiang@intel.com>
Cc: "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
List-Id: xen-devel@lists.xenproject.org

On 12/19/2009 06:47 AM, Jiang, Yunhong wrote:
>>> +
>>> +#define XENPF_mem_hotadd    59
>>> +struct xenpf_mem_hotadd {
>>> +	uint64_t spfn;
>>> +	uint64_t epfn;
>>> +	uint32_t pxm;
>>> +	uint32_t flags;
>>> +};
>>> +
>>>   struct xen_platform_op {
>>>   	uint32_t cmd;
>>>   	uint32_t interface_version; /* XENPF_INTERFACE_VERSION */
>>> @@ -362,6 +371,7 @@ struct xen_platform_op {
>>>   		struct xenpf_pcpuinfo          pcpu_info;
>>>   		struct xenpf_cpu_ol            cpu_ol;
>>>   		struct xenpf_cpu_hotadd        cpu_add;
>>> +		struct xenpf_mem_hotadd        mem_add;
>>>   		uint8_t                        pad[128];
>>>        
>> Should the size of the pad be decreased?
>>      
> This is defined by xen hypervisor, and is intended for extenstion in future, I think.
>    

But Konrad's point is that if you have padding to reserve space for 
future expansion, shouldn't you decrease the padding when you actually 
increase the structure?  Otherwise, if you can arbitrarily grow the 
structure, why do you need padding?

     J