Re: [PATCH v5 00/21] Add support for qemu-xen runnning in a Linux-based stubdomain

[Jason Andryuk <jandryuk@xxxxxxxxx>]

Ping?

-Jason

On Tue, Apr 28, 2020 at 12:05 AM Jason Andryuk <jandryuk@xxxxxxxxx> wrote:
>
> Hi,
>
> In coordination with Marek, I'm making a submission of his patches for Linux
> stubdomain device-model support.  I made a few of my own additions, but Marek
> did the heavy lifting.  Thank you, Marek.
>
> Below is mostly the v4 cover leter with a few additions.
>
> General idea is to allow freely set device_model_version and
> device_model_stubdomain_override and choose the right options based on this
> choice.  Also, allow to specific path to stubdomain kernel/ramdisk, for 
> greater
> flexibility.
>
> First two patches add documentation about expected toolstack-stubdomain-qemu
> interface, both for MiniOS stubdomain and Linux stubdomain.
>
> Initial version has no QMP support - in initial patches it is completely
> disabled, which means no suspend/restore and no PCI passthrough.
>
> Later patches add QMP over libvchan connection support. The actual connection
> is made in a separate process. As discussed on Xen Summit 2019, this allows to
> apply some basic checks and/or filtering (not part of this series), to limit
> libxl exposure for potentially malicious stubdomain.
>
> Jason's additions ensure the qmp-proxy (vchan-socket-proxy) processes and
> sockets are cleaned up and add some documentation.
>
> The actual stubdomain implementation is here:
>
>     https://github.com/marmarek/qubes-vmm-xen-stubdom-linux
>     (branch for-upstream, tag for-upstream-v3)
>
> See readme there for build instructions.  Marek's version requires dracut.  I
> have hacked up a version usable install with initramfs-tools:
>
>    https://github.com/jandryuk/qubes-vmm-xen-stubdom-linux
>    (branch initramfs-tools)
>
> Few comments/questions about the stubdomain code:
>
> 1. There are extra patches for qemu that are necessary to run it in 
> stubdomain.
> While it is desirable to upstream them, I think it can be done after merging
> libxl part. Stubdomain's qemu build will in most cases be separate anyway, to
> limit qemu's dependencies (so the stubdomain size).
>
> 2. By default Linux hvc-xen console frontend is unreliable for data transfer
> (qemu state save/restore) - it drops data sent faster than client is reading
> it. To fix it, console device needs to be switched into raw mode (`stty raw
> /dev/hvc1`). Especially for restoring qemu state it is tricky, as it would 
> need
> to be done before opening the device, but stty (obviously) needs to open the
> device first. To solve this problem, for now the repository contains kernel
> patch which changes the default for all hvc consoles. Again, this isn't
> practical problem, as the kernel for stubdomain is built separately. But it
> would be nice to have something working with vanilla kernel. I see those
> options:
>   - convert it to kernel cmdline parameter (hvc_console_raw=1 ?)
>   - use channels instead of consoles (and on the kernel side change the 
> default
>     to "raw" only for channels); while in theory better design, libxl part 
> will
>     be more complex, as channels can be connected to sockets but not files, so
>     libxl would need to read/write to it exactly when qemu write/read the 
> data,
>     not before/after as it is done now
>
> 3. Mini-OS stubdoms use dmargs xenstore key as a string.  Linux stubdoms use
> dmargs as a directory for numbered entries.  Should they be different names?
>
> Remaining parts for eliminating dom0's instance of qemu:
>  - do not force QDISK backend for CDROM
>  - multiple consoles support in xenconsoled
>
> Changes in v2:
>  - apply review comments by Jason Andryuk
> Changes in v3:
>  - rework qemu arguments handling (separate xenstore keys, instead of \x1b 
> separator)
>  - add QMP over libvchan, instead of console
>  - add protocol documentation
>  - a lot of minor changes, see individual patches for full changes list
>  - split xenconsoled patches into separate series
> Changes in v4:
>  - extract vchan connection into a separate process
>  - rebase on master
>  - various fixes
> Changes in v5:
>  - Marek: apply review comments from Jason Andryuk
>  - Jason: Clean up qmp-proxy processes and sockets
>
> Cc: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
> Cc: Simon Gaiser <simon@xxxxxxxxxxxxxxxxxxxxxx>
> Cc: Eric Shelton <eshelton@xxxxxxxxx>
> Cc: Ian Jackson <ian.jackson@xxxxxxxxxx>
> Cc: Wei Liu <wl@xxxxxxx>
>
> Eric Shelton (1):
>   libxl: Handle Linux stubdomain specific QEMU options.
>
> Jason Andryuk (5):
>   docs: Add device-model-domid to xenstore-paths
>   libxl: Check stubdomain kernel & ramdisk presence
>   libxl: Refactor kill_device_model to libxl__kill_xs_path
>   libxl: Kill vchan-socket-proxy when cleaning up qmp
>   tools: Clean up vchan-socket-proxy socket
>
> Marek Marczykowski-Górecki (15):
>   Document ioemu MiniOS stubdomain protocol
>   Document ioemu Linux stubdomain protocol
>   libxl: fix qemu-trad cmdline for no sdl/vnc case
>   libxl: Allow running qemu-xen in stubdomain
>   libxl: write qemu arguments into separate xenstore keys
>   xl: add stubdomain related options to xl config parser
>   tools/libvchan: notify server when client is connected
>   libxl: add save/restore support for qemu-xen in stubdomain
>   tools: add missing libxenvchan cflags
>   tools: add simple vchan-socket-proxy
>   libxl: use vchan for QMP access with Linux stubdomain
>   Regenerate autotools files
>   libxl: require qemu in dom0 even if stubdomain is in use
>   libxl: ignore emulated IDE disks beyond the first 4
>   libxl: consider also qemu in stubdomain in libxl__dm_active check
>
>  .gitignore                          |   1 +
>  configure                           |  14 +-
>  docs/configure                      |  14 +-
>  docs/man/xl.cfg.5.pod.in            |  27 +-
>  docs/misc/stubdom.txt               | 103 ++++++
>  docs/misc/xenstore-paths.pandoc     |   5 +
>  stubdom/configure                   |  14 +-
>  tools/Rules.mk                      |   2 +-
>  tools/config.h.in                   |   3 +
>  tools/configure                     |  46 ++-
>  tools/configure.ac                  |   9 +
>  tools/libvchan/Makefile             |   8 +-
>  tools/libvchan/init.c               |   3 +
>  tools/libvchan/vchan-socket-proxy.c | 500 ++++++++++++++++++++++++++++
>  tools/libxl/libxl_aoutils.c         |  32 ++
>  tools/libxl/libxl_create.c          |  46 ++-
>  tools/libxl/libxl_dm.c              | 484 +++++++++++++++++++++------
>  tools/libxl/libxl_domain.c          |   7 +
>  tools/libxl/libxl_internal.h        |  22 ++
>  tools/libxl/libxl_mem.c             |   6 +-
>  tools/libxl/libxl_qmp.c             |  27 +-
>  tools/libxl/libxl_types.idl         |   3 +
>  tools/xl/xl_parse.c                 |   7 +
>  23 files changed, 1205 insertions(+), 178 deletions(-)
>  create mode 100644 tools/libvchan/vchan-socket-proxy.c
>
> --
> 2.20.1
>