Re: [Qemu-devel] About the light VM solution!

[Stefan Hajnoczi]

On Wed, Dec 06, 2017 at 09:21:55AM +0000, Gonglei (Arei) wrote:
> 
> > -----Original Message-----
> > From: Qemu-devel
> > [mailto:address@hidden On
> > Behalf Of Stefan Hajnoczi
> > Sent: Wednesday, December 06, 2017 12:31 AM
> > To: Paolo Bonzini
> > Cc: Yang Zhong; Stefan Hajnoczi; qemu-devel
> > Subject: Re: [Qemu-devel] About the light VM solution!
> > 
> > On Tue, Dec 05, 2017 at 03:00:10PM +0100, Paolo Bonzini wrote:
> > > On 05/12/2017 14:47, Stefan Hajnoczi wrote:
> > > > On Tue, Dec 5, 2017 at 1:35 PM, Paolo Bonzini <address@hidden>
> > wrote:
> > > >> On 05/12/2017 13:06, Stefan Hajnoczi wrote:
> > > >>> On Tue, Dec 05, 2017 at 02:33:13PM +0800, Yang Zhong wrote:
> > > >>>> As you know, AWS has decided to switch to KVM in their clouds. This
> > news make almost all
> > > >>>> china CSPs(clouds service provider) pay more attention on KVM/Qemu,
> > especially light VM
> > > >>>> solution.
> > > >>>>
> > > >>>> Below are intel solution for light VM, qemu-lite.
> > > >>>>
> > http://events.linuxfoundation.org/sites/events/files/slides/Light%20weight%2
> > 0virtualization%20with%20QEMU%26KVM_0.pdf
> > > >>>>
> > > >>>> My question is whether community has some plan to implement light
> > VM or alternative solutions? If no, whether our
> > > >>>> qemu-lite solution is suitable for upstream again? Many thanks!
> > > >>>
> > > >>> What caused a lot of discussion and held back progress was the 
> > > >>> approach
> > > >>> that was taken.  The basic philosophy seems to be bypassing or
> > > >>> special-casing components in order to avoid slow operations.  This
> > > >>> requires special QEMU, firmware, and/or guest kernel binaries and
> > causes
> > > >>> extra work for the management stack, distributions, and testers.
> > > >>
> > > >> I think having a special firmware (be it qboot or a special-purpose
> > > >> SeaBIOS) is acceptable.
> > > >
> > > > The work Marc Mari Barcelo did in 2015 showed that SeaBIOS can boot
> > > > guests quickly.  The guest kernel was entered in <35 milliseconds
> > > > IIRC.  Why is special firmware necessary?
> > >
> > > I thought that wasn't the "conventional" SeaBIOS, but rather one with
> > > reduced configuration options, but I may be remembering wrong.
> > 
> > Marc didn't spend much time on optimizing SeaBIOS, he used the build
> > options that were suggested.  An extra flag can be added in
> > qemu_preinit() to skip slow init that's unnecessary on optimized
> > machines.  That would allow a single SeaBIOS binary to run both full and
> > lite systems.
> > 
> What's options do you remember? Stefan. Or any links about that
> thread? I'm Interesting with this topic.

Here is what I found:

Marc Mari's fastest SeaBIOS build took 8 ms from the first guest CPU
instruction to entering the guest kernel.  CBFS was used instead of a
normal boot device (e.g. virtio-blk).  Most hardware support was
disabled.

https://mail.coreboot.org/pipermail/seabios/2015-July/009554.html

The SeaBIOS configuration file is here:

https://mail.coreboot.org/pipermail/seabios/2015-July/009548.html

Stefan

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