Re: shared memory and event channel

[Keir Fraser <Keir.Fraser@cl.cam.ac.uk>]

It's a special-case type of inter-domain event channel in which one end is
connected to Xen itself rather than the guest. It's actually only used for
the per-vcpu ioemu event-channel that HVM guests require.

 -- Keir

On 21/12/07 08:39, "tgh" <wwwwww4187@sina.com.cn> wrote:

> hi
>   I read the code of eventchannel,and I am confused by the viarable
> named as"consumer_is_xen"in the evtchn struct, what is the function of
> consumer_is_xen? and does dom use eventchannel to communicate with
> hypervisor? why not the hypercall? and in which condition is
> eventchannel used in this way,that is ,the dom issues an event to
> hypervisor or xen,and xen is a consumer?
> 
> Thanks in advance
> 
> 
> 
> 
> Mark Williamson 写道:
>>>    For each domUs there is unique shared memory(2-way circular queue) and
>>> event-channel(one shared memory and event-channel per domU) or there is
>>> only one shared memory and interdomain event-channel(for every DomU)?
>>>     
>> 
>> Each domain has a separate shared memory page and event channel.  Actually,
>> in 
>> general, there are multiple shared memory areas and event channels per domU.
>> 
>> Each virtual device (e.g. virtual network interface) may require its own
>> separate shared memory page and event channel to talk to the backend.  So if
>> you have a domain with two vifs it'll need two shared memory pages and two
>> event channels.
>> 
>> The block driver will also want a memory page and event channel for each
>> virtual block device.
>> 
>> And so on.
>> 
>> Hope this helps,
>> 
>> Cheers,
>> Mark
>> 
>>   
> 
> 
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