GSoC'20 Interested Student: Adding support to Jailhouse Hypervisor
PRAKHAR BANSAL
prakharbansal0910 at gmail.com
Tue Mar 31 02:43:15 UTC 2020
Hi Jan,
Thanks for the confirmation to proceed on project proposal.
Also, I tried installing Jailhouse on my VM after enabling VT-x/EPT and
IOMMU for my VM(Guest OS- Ubuntu 18.04) on VMware fusion hypervisor with
MacOS on the host side.
However, Jailhouse hardware check was failed because of missing
*Preemption timer
and Virtualize APIC access*, could you please suggest, if this is hardware
limitation? Is there any workaround here?
My laptop's processor is Intel quad-core i7.
[image: image.png]
Also, could you please suggest, if I can talk to you through an IRC or
slack channel since it is a bit hard to communicate over email every time.
Thanks,
Prakhar
On Mon, Mar 30, 2020 at 6:15 AM Jan Kiszka <jan.kiszka at web.de> wrote:
> On 30.03.20 10:02, PRAKHAR BANSAL wrote:
> > Hi Jan,
> >
> > On Sat, Mar 28, 2020 at 4:12 AM Jan Kiszka <jan.kiszka at web.de
> > <mailto:jan.kiszka at web.de>> wrote:
> >
> > On 28.03.20 08:47, PRAKHAR BANSAL wrote:
> > > Hi Jan,
> > >
> > > Thanks for the reply!
> > >
> > > I was only considering the command-line tool "code" for reference
> > to the
> > > Jailhouse kernel API(ioctl calls) because I didn't find a
> > documentation
> > > of the Jailhouse kernel APIs.
> >
> > Right, the IOCTL API is not documented so far. It is currently only
> used
> > inside the Jailhouse project. This needs to be formalized when there
> > shall be external users like a libvirt driver.
> >
> > That might be a nice small contribution task: Create some
> > Documentation/driver-interfaces.md that describes the IOCTLs along
> with
> > their parameter structures and that also includes the current
> > sysfs-entries.txt as a section. Then send this as patch here. I'll
> help
> > out when details are not clear from reading the code.
> >
> > Sure. I will do that.
> >
> > >
> > > For the second part as you mentioned that Jailhouse can only
> create
> > > cells with the constraints defined in the root cell
> configuration. I
> > > have a few questions regarding that.
> > >
> > > 1. Is there a way to know if Jailhouse is enabled on the host and
> get
> > > the root cell configuration(s) from Jailhouse through an API?
> > This can
> > > be used while binding the libvirt to the Jailhouse hypervisor.
> >
> > Look at
> >
> https://github.com/siemens/jailhouse/blob/master/Documentation/sysfs-entries.txt
> > for what is reported as runtime information. Full configurations
> can't
> > be read back at this point. This might be reconsidered in the light
> of
> > [1], but I wouldn't plat for that yet.
> >
> >
> > Ok, sure. I am looking into it.
> >
> >
> > >
> > > 2. If Jailhouse is not enabled(again can we know this using some
> API)
> > > then, can libvirt enable/disable Jailhouse during the libvirt
> > binding of
> > > the Jailhouse driver with a given set of Jailhouse cell
> > configurations
> > > describing a complete partitioned system?
> >
> > With the API above and a given configuration set, yes. The config set
> > would have to be provided to the libvirt driver in some to-be-defined
> > way (e.g. /etc/libvirt/jailhouse.conf ->
> /etc/libvirt/jailhouse/*.cell).
> >
> > Cool, got it. Thanks!
> >
> > >
> > > 3. I was wondering, as you mentioned that libvirt driver should
> check
> > > for mismatch of the cell configuration with the root cell
> > configuration,
> > > the question is, isn't that done by Jailhouse itself? If yes, then
> > > libvirt can just pass on the cell creation requests to Jailhouse
> and
> > > return the response to the user as it is, rather than driver
> > doing any
> > > such mismatch check.
> >
> > With matching I'm referring to a libvirt user request like "create a
> > domain with 2 CPUs", while there are no cells left that have more
> than
> > one CPU. Or "give the domain 1G RAM", and you need to find an
> available
> > cell with that much memory. Those are simple examples. A request that
> > states "connect the domain to the host network A" implies that a cell
> > has a shared-memory link to, say, the root cell that can be
> configured
> > to bridge this. But let's keep that for later and start as simple as
> > possible.
> >
> >
> > Do I need to match the libvirt user-requested cell config with only root
> > cells or with all cells present at that time?
>
> With all non-root cells - the root cell will be occupied already (it
> runs libvirt e.g.).
>
> >
> > I wanted to request you for a favor for the proposal as the deadline is
> > approaching. Could I prepare a proposal for this project based on our
> > discussion here and improve it later based on feedback comments after
> > the deadline? I understand that I got late in starting on the project
> > search and selection.
>
> Sure, please go ahead.
>
> Jan
>
> >
> > Thanks,
> > Prakhar
> >
> >
> > Jan
> >
> > [1]
> >
> https://groups.google.com/d/msgid/jailhouse-dev/CADiTV-1QiRhSWZnw%2BkHhJMO-BoA4sAcOmTkQE7ZWbHkGh3Jexw%40mail.gmail.com
> >
> > >
> > > -Prakhar
> > >
> > > On Thu, Mar 26, 2020 at 1:49 AM Jan Kiszka <jan.kiszka at web.de
> > <mailto:jan.kiszka at web.de>
> > > <mailto:jan.kiszka at web.de <mailto:jan.kiszka at web.de>>> wrote:
> > >
> > > Hi Prakhar,
> > >
> > > On 25.03.20 05:36, PRAKHAR BANSAL wrote:
> > > > Hi Jan,
> > > >
> > > > Thanks for the reply. I looked deeper into the libvirt and
> > Jailhouse
> > > > source code and found following two things that seem
> > relevant to the
> > > > project I am interested in.
> > > >
> > > > - Libvirt driver interface at [libvirt.git]
> > > > <https://libvirt.org/git/?p=libvirt.git;a=tree;hb=HEAD> /
> src
> > > >
> > <https://libvirt.org/git/?p=libvirt.git;a=tree;f=src;hb=HEAD> /
> > > driver.h
> > > >
> > >
> > <
> https://libvirt.org/git/?p=libvirt.git;a=blob_plain;f=src/driver.h;hb=HEAD
> >
> > > > - Jailhouse tool, which is using the ioctl API of the
> > Jailhouse,
> > > > available at
> > > >
> > https://github.com/siemens/jailhouse/blob/master/tools/jailhouse.c.
> > > >
> > > > With the help of the above two, it looks like, a libvirt
> > driver
> > > for the
> > > > Jailhouse can be implemented. Let me know if I am moving
> > in the right
> > > > direction so far.
> > >
> > > From the Jailhouse perspective, it is important to not
> > consider the
> > > command line tool an interface anymore (like in the first
> > prototype) but
> > > build on top of the Linux driver API (ioctls, sysfs). There
> > is already a
> > > Python library which started to abstract this interface for
> > > Jailhouse-internal use cases. However, I strongly suspect
> > libvirt will
> > > rather want a native binding.
> > >
> > > >
> > > > I have been looking at the other libvirt driver
> > implementations for
> > > > hypervisors like HyperV and VMware to understand their
> > implementation
> > > > and learn from there.
> > >
> > > As Jailhouse is a static partitioning hypervisor without
> > abstraction of
> > > the underlying hardware, your starting point for the libvirt
> > binding
> > > should be a given set of Jailhouse cell configurations
> > describing a
> > > complete partitioned system. So rather than instantiating on
> > demand a
> > > domain (Jailhouse cell) with, say, a network adapter, the
> > driver should
> > > match a user request for a domain against the configuration
> > set and use
> > > what is there - or report the mismatch. What it could
> > organize, though,
> > > is interconnecting cells that have a (preconfigured) virtual
> > network
> > > link to the root cell.
> > >
> > > Due to this different concept, there will be no 1:1 mapping
> for
> > > commodity hypervisor drivers to the Jailhouse scenario.
> > Still, studying
> > > what they do is useful and needed in order to understand what
> > "normally"
> > > happens and find a reasonable translation. This is probably
> > the most
> > > challenging part of the project.
> > >
> > > Jan
> > >
> >
>
>
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