From mboxrd@z Thu Jan  1 00:00:00 1970
From: Wen Congyang <wency@cn.fujitsu.com>
Subject: Re: [RFC Patch v3 03/18] don't zero out ioreq page
Date: Fri, 12 Sep 2014 15:33:49 +0800
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To: David Vrabel <david.vrabel@citrix.com>, xen devel <xen-devel@lists.xen.org>
Cc: Ian Campbell <Ian.Campbell@citrix.com>, Ian Jackson <Ian.Jackson@eu.citrix.com>, Jiang Yunhong <yunhong.jiang@intel.com>, Dong Eddie <eddie.dong@intel.com>, Paul Durrant <paul.durrant@citrix.com>, Yang Hongyang <yanghy@cn.fujitsu.com>, Lai Jiangshan <laijs@cn.fujitsu.com>
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On 09/05/2014 06:45 PM, David Vrabel wrote:
> On 05/09/14 10:10, Wen Congyang wrote:
>> ioreq page may contain some pending I/O requests, and we need to
>> handle the pending I/O req after migration.
>>
>> TODO:
>> 1. update qemu to handle the pending I/O req
> 
> Under what conditions can there be pending I/O?  A domain suspend should
> not complete until any I/O accesses are complete.

IIRC, I print ioreq.state after suspending vm, and ioreq.state can be
STATE_IOREQ_NONE, STATE_IOREQ_READY or STATE_IORESP_READY. If the
state is STATE_IOREQ_READY, we should kick vcpu event channel on resume
after migration.

But I test it again today, the state is always STATE_IOREQ_NONE...

If the state is always STATE_IOREQ_NONE, no need to touch hypervisor/Qemu
to handle pending I/O req(state is STATE_IOREQ_READY).

Thanks
Wen Congyang

> 
> Suspending a domain that's part-way through an instruction seems mad to
> me -- how are you supposed to capture this sort of state?
> 
> David
> .
>