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Date: Mon, 5 Feb 2018 18:36:31 +0000
From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Message-ID: <20180205183630.GD2317@work-vm>
References: <1517842735-9011-1-git-send-email-jianfeng.tan@intel.com>
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In-Reply-To: <ae1c99ba-260e-bdfb-4f36-908271d4b46e@intel.com>
Subject: Re: [Qemu-devel] [RFC] exec: eliminate ram naming issue as migration
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To: "Tan, Jianfeng" <jianfeng.tan@intel.com>
Cc: Igor Mammedov <imammedo@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, Jason Wang <jasowang@redhat.com>, Maxime Coquelin <maxime.coquelin@redhat.com>, qemu-devel@nongnu.org, "Michael S . Tsirkin" <mst@redhat.com>

* Tan, Jianfeng (jianfeng.tan@intel.com) wrote:
> 
> 
> On 2/6/2018 12:29 AM, Igor Mammedov wrote:
> > On Mon,  5 Feb 2018 14:58:55 +0000
> > Jianfeng Tan <jianfeng.tan@intel.com> wrote:
> > 
> > > Existing VMs with virtio devices and vhost-kernel as the backend
> > > are always started with mem config:
> > > 
> > >    "-m xG"
> > >    (with a ram block named "pc.ram")
> > > 
> > > while new VMs with virtio devices and vhost-user as the backend
> > > are always started with mem config:
> > > 
> > >    "-m xG -numa node,memdev=pc.ram -object memory-backend-file,id=pc.ram,..."
> > >    (with a ram block named "/object/pc.ram")
> > could you elaborate more on what src command line migrating to what dst command line?
> 
> The src cmdline:
>     $QEMU -enable-kvm -cpu host -smp 4 /path/to/img \
>       -m 2G \
>       -netdev tap,id=mynet1,vhost=on \
>       -device virtio-net-pci,netdev=mynet1,mac=52:54:00:12:34:58 ...
> 
> The dst cmdline:
>     $QEMU -enable-kvm -cpu host -smp 4 /path/to/img \
>       -m 2G -numa node,memdev=pc.ram -mem-prealloc \
>       -object
> memory-backend-file,id=pc.ram,size=2G,mem-path=/dev/hugepages,share=on \
>       -chardev socket,id=char0,path=/tmp/sock0 \
>       -netdev type=vhost-user,id=mynet1,chardev=char0,vhostforce \
>       -device virtio-net-pci,netdev=mynet1,mac=52:54:00:12:34:58 \
>       -incoming tcp:0:4444 ...

I'm surprised that it's safe to -numa node  the destination, even with
the hack to the RAMBlock naming.  I'd expect it to have other effects
as well.

Dave

> Thanks,
> Jianfeng
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK