[Kata-hypervisor] Link to the Hypervisor Prototype

Jon Olson jonolson at google.com
Wed Jun 6 23:47:41 UTC 2018


(note: currently at an off-site: responses may be delayed or worse)

The interest that I had (and at the risk of speaking for him and being
corrected, I think Ben as well) was in a VM *shape* focussed on something
suitable for containers. In particular something based on a modern set of
hardware features and minimizing the need for emulation of anything (PITs,
PICs, PCI controllers, etc.)

I would agree that for what qemu does that it's hard to do better, but
we're actively uninterested in many of the things qemu does being supported
by our offering. They don't help workloads we care about and they present
"challenging" surface areas from a security perspective.

Note that Google does actually have such a VM, aimed at containers and open
source, implemented in Rust for Chrome OS. We are not using it in Cloud
currently (and to be honest I haven't dived into it beyond being highly
amused at the horrifying kernel command line that explicitly MMIO maps app
of their virtio devices). This was on a production Pixel book, so nothing
fancy or proprietary going on there.

Jon

On Wed, Jun 6, 2018, 4:14 PM Anthony Liguori <aliguori at amazon.com> wrote:

> "Jessie Frazelle (TUPPERWARE)" <jessfraz at microsoft.com> writes:
>
> > Sorry outlook cut off the first line... windows...
> >
> > so rust :D
>
> I was able to join the prep call at least and I raised this during that
> discussion.  I'm not sure what problem this group is trying to tackle.
>
> What was brought up on the call is a "cloud VMM" as an alternative to
> QEMU but I don't really agree with that premise.  For the problem space
> that QEMU tackles, it's hard to do better than it does and it tackles a
> huge space.
>
> Cloud is an extremely ambiguous term too.  In another part of this
> thread, qcow2 was mentioned as a target which I don't think at all is
> something that is interesting if you are an infrastructure provider.
>
> There's lot of stuff that I am interested in (particularly around super
> fast start up time and super low overhead to get high density) but
> that's only possible to achieve if you constrain the problem space
> tremendously.
>
> Regards,
>
> Anthony Liguori
>
> >
> > ________________________________________
> > From: Jessie Frazelle (TUPPERWARE) <jessfraz at microsoft.com>
> > Sent: Wednesday, June 6, 2018 6:37 PM
> > To: Anthony Liguori; Ernst, Eric; Sasha Levin; Manohar Castelino
> > Cc: kata-hypervisor at lists.katacontainers.io
> > Subject: Re: [Kata-hypervisor] Link to the Hypervisor Prototype
> >
> > Rust?
> >
> > What would you do?
> >
> > ________________________________________
> > From: Anthony Liguori <aliguori at amazon.com>
> > Sent: Wednesday, June 6, 2018 6:36 PM
> > To: Jessie Frazelle (TUPPERWARE); Ernst, Eric; Sasha Levin; Manohar
> Castelino
> > Cc: kata-hypervisor at lists.katacontainers.io
> > Subject: Re: [Kata-hypervisor] Link to the Hypervisor Prototype
> >
> > "Jessie Frazelle (TUPPERWARE)" <jessfraz at microsoft.com> writes:
> >
> >> Anthony,
> >>
> >> Would you be willing to dedicate resources to a _hypothetical_ rewrite
> >> of that layer that we could replace qemu with in the form of a go
> >> library?
> >>
> >> 0:)
> >
> > Go is so 2015.  Rust is where it's at now :-)
> >
> > In all seriousness, I've always felt strongly that a device model needs
> > to avoid garbage collection.  While it's not strictly a real time
> > system, OSes have an expectation that PIO or MMIO operations have an
> > upper bound of latency.
> >
> > The other challenge with Go is unpredictable memory usage due to
> > automatic heap growth.  If you want to do planning around density, being
> > able to rationalize about the memory overhead from the VMM layer is
> > pretty important.
> >
> > Regards,
> >
> > Anthony Liguori
> >
> >>
> >>
> >>
> >> ________________________________________
> >> From: Anthony Liguori <aliguori at amazon.com>
> >> Sent: Wednesday, June 6, 2018 5:00 PM
> >> To: Ernst, Eric; Sasha Levin; Manohar Castelino
> >> Cc: kata-hypervisor at lists.katacontainers.io
> >> Subject: Re: [Kata-hypervisor] Link to the Hypervisor Prototype
> >>
> >> "Ernst, Eric" <eric.ernst at intel.com> writes:
> >>
> >>> Hey Sasha, Anthony –
> >>>
> >>> I want to set a bit of context here.  At the face to face discussion
> >>> in Vancouver, we had agreed to share the prototyping we have put in
> >>> place to better understand how far we could go to remove legacy, and
> >>> minimize the number of device models, while still booting key
> >>> workloads.  Manohar’s response is to address the action that everyone
> >>> in the meeting requested.
> >>
> >> Yup, appreciate the sharing and am disappointed I wasn't able to attend
> >> in person.  I'm sure Paolo gave you lots of great feedback but let me
> >> expand a bit on why I think this is the wrong approach.  Ultimately, you
> >> are certainly free to continue down this path though but just thought
> >> you may find this useful.
> >>
> >> The pieces of QEMU that are easy to remove are largely already
> >> configurable at build time.  From a practical perspective, if you build
> >> your "prototype" and measure the resulting executable size compared to a
> >> minimalistic configuration, you will find very little actual reduction
> >> in code.
> >>
> >> The stuff that's hard to remove is deeply ingrained (like QMP and QOM)
> >> or parts that are just hairy (like vl.c).  Years of effort have gone
> >> into decoupling these bits.
> >>
> >> So you get very little actual benefit (in code size reduction) by
> >> forking but get to bare the burden of independent maintenance.
> >>
> >> Regards,
> >>
> >> Anthony Liguori
> >>
> >>
> >>>
> >>> Cheers,
> >>> Eric
> >>>
> >>> On 6/6/18, 1:46 PM, "Sasha Levin" <Alexander.Levin at microsoft.com>
> wrote:
> >>>
> >>>     On Wed, Jun 06, 2018 at 08:08:46PM +0000, Castelino, Manohar R
> wrote:
> >>>     >Folks,
> >>>     >
> >>>     >Please find below the link to the initial prototype code that
> tries to reduce the number of emulated devices in QEMU that can still boot
> most cloud workloads.
> >>>     [snip]
> >>>
> >>>     Out of curiousity, have you looked at kvmtool
> >>>     (
> https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.kernel.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Fwill%2Fkvmtool.git%2F&data=02%7C01%7Cjessfraz%40microsoft.com%7C604dbe2ada034e62d2f908d5cbf07f6b%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636639156156262890&sdata=xEWVp9B0rIFl5Ez1cGTMz9ClFs5Ril%2FTJN2SgVta824%3D&reserved=0
> )?
> >>>
> >>>     Forking qemu rather than building on top of it (or using something
> else)
> >>>     isn't going to end well IMO.
> >>>     _______________________________________________
> >>>     Kata-hypervisor mailing list
> >>>     Kata-hypervisor at lists.katacontainers.io
> >>>
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> >>>
> >>>
> >>> _______________________________________________
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> >>>
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> >>
> >> _______________________________________________
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> >> Kata-hypervisor at lists.katacontainers.io
> >>
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> >
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> >
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