[dpdk-dev] [PATCH] vhost: enable live migration

[Long, Thomas]

> -----Original Message-----
> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Thomas Monjalon
> Sent: Thursday, June 4, 2015 2:00 PM
> To: Xie, Huawei
> Cc: dev at dpdk.org
> Subject: Re: [dpdk-dev] [PATCH] vhost: enable live migration

> 2015-06-01 04:47, Ouyang, Changchun:
> >  From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Huawei Xie
> > > When we migrate VM, without this feature, qemu will report error :
> > > "migrate: Migration disabled: vhost lacks VHOST_F_LOG_ALL feature".
> > 
> > Is this enough for vhost to support  migrate VM?
> > I remember Claire has another patch, possibly need refer to that patch.

> Indeed, there were some patches which do not build:
> 	http://dpdk.org/ml/archives/dev/2014-August/005050.html
> And there was no answer.

The log name is incorrect in Claire's patch and "CONFIG" needs to replaced with "VHOST_CONFIG". It also only supported migration for vhost_cuse. Claire left the org around the same time and the patch was not picked up



> [...]
> > > +				(1ULL << VHOST_F_LOG_ALL))

> Please check if this line is sufficient.

This should be sufficient to enable migration for vhost-user. 

The previous patch with the CONFIG log fix enables migration for vhost-cuse. The behavior of qemu with vhost_cuse when migrating is to turn on the migration flag before migration regardless of what the backend advertises as being supported and to disable it again once migration has been completed. This is why Claire's patch ignores the VHOST_F_LOG_ALL setting although I don't think this is the right way to implement this.  If the current patch is combined with the vhost_net_ioctl modifications of the original patch then it should enable migration for both vhost-cuse and vhost-user. 

> Thanks