Re: Rebooting domu fails in nfs share exported from another domu on the same dom0

[annie li <annie.li@oracle.com>]

On 2014/7/18 16:22, Konrad Rzeszutek Wilk wrote:
> On Fri, Jul 18, 2014 at 04:17:02PM -0400, annie li wrote:
>> On 2014/7/18 15:43, Konrad Rzeszutek Wilk wrote:
>>> On Fri, Jul 18, 2014 at 03:31:43PM -0400, annie li wrote:
>>>> On 2014/7/18 14:53, Konrad Rzeszutek Wilk wrote:
>>>>> On Thu, Jul 17, 2014 at 12:56:12PM -0400, annie li wrote:
>>>>>> On 2014/7/17 11:49, Roger Pau Monné wrote:
>>>>>>> On 16/07/14 22:36, annie li wrote:
>>>>>>>> Hi
>>>>>>>>
>>>>>>>> I hit a problem in such scenario: vm1 is running and export nfs service,
>>>>>>>> dom0 mount this nfs, and vm2 is booted in this nfs location. vm1 and vm2
>>>>>>>> are running on the same dom0.
>>>>>>>>
>>>>>>>> When this bug happens, the data flow is:  vm2 blkfront-> vm2 blkback->
>>>>> I am a bit confused here. 'vm2 blkfront -> vm2 blkback'? Did you
>>>>> mean 'dom0 blkback'?
>>>> Yes, Dom0 blkback.
>>>>
>>>>>>>> loop -> nfs file -> nfs client -> bridge priv1 -> vm1 vif -> vm1 netback
>>>>>>>> -> vm1 netfront.
>>>>> So both netback and netfront run in the same guest? I think you
>>>>> want these two swapped around (netfront -> netback).
>>>> No, the netfront in above routine means the one in guest vm1, and this is
>>>> network RX path in vm1.
>>> OK, so 'dom0 netback' then. As the netback thread is running in the
>>> initial domain?
>> Netback thread is running in Dom0 as normal, and the two vms are all
>> normal vm, not driver domain. Probably my initial description causes
>> some confusion.
>>
>>> So a revised view is:
>>>
>>>    vm2 blkfront -> dom0 blkback -> loop -> nfs file -> nfs client
>>> 	-> bridge priv1 -> vm1 vif -> dom0 netback -> vm1 netfront
>>>
>>> So with the grant map (blkfront -> blkback) the source is dom0
>>> and the destination is vm1.
>> You mean destination is vm2 here, right?
> Yes :-)
>> But I am little confused. Blkfront of vm2 sends out request to
>> blkback, and the data page is allocated from vm2. So the grant map
>> source is vm2, destination is dom0. Anything I missed here?
>>
>>>   For the grant copy, the source is
>>> dom0 and the destinatation is vm2 right? (or did I get my src
>>> and dst confused?).
>> You mean vm1 here, right?
> Heh.
>> If so, yes, source is dom0, and destination is vm1.
>> In grantcopy code, it checks whether the source is from dom0, if
>> not, then an error is thrown out. In this situation, the source is
>> from vm2 which is grant mapped.
> In both cases dom0 is part of the equation. In one
> case it is the destination and in another it is the source - both cases
> for the same page right?

Yes.
blkfront->blkback, dom0 is destination
netback->netfront, dom0 is the source

When doing grantcopy for netback, xen requires the source is dom0. 
However, it is vm2 in this case.

Thanks
Annie

>
>> Thanks
>> Annie
>>>
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