Hi Roman On Thu, Oct 31, 2024 at 3:12 PM Roman Penyaev <r.peni...@gmail.com> wrote:
> Hi Marc-André, > > In this 5th version of the mux-be series it seems I addressed all the > comments and concerns. Could you please take a look once again? > > I am not sure adding a "mux-be-id" option to all chardevs is the way to go. To me it feels like working around the issue that arrays are not supported on the CLI. I would like others to comment.. > -- > Roman > > On Thu, Oct 17, 2024 at 4:45 PM Roman Penyaev <r.peni...@gmail.com> wrote: > > > > Mux is a character backend (host side) device, which multiplexes > > multiple frontends with one backend device. The following is a > > few lines from the QEMU manpage [1]: > > > > A multiplexer is a "1:N" device, and here the "1" end is your > > specified chardev backend, and the "N" end is the various parts > > of QEMU that can talk to a chardev. > > > > But sadly multiple backends are not supported. > > > > This work implements multiplexing capability of several backend > > devices, which opens up an opportunity to use a single frontend > > device on the guest, which can be manipulated from several > > backend devices. > > > > The motivation is the EVE project [2], where it would be very > > convenient to have a virtio console frontend device on the guest that > > can be controlled from multiple backend devices, namely VNC and local > > TTY emulator. The following is an example of the QEMU command line: > > > > -chardev mux-be,id=mux0 \ > > -chardev > socket,path=/tmp/sock,server=on,wait=off,id=sock0,mux-be-id=mux0 \ > > -chardev vc,id=vc0,mux-be-id=mux0 \ > > -device virtconsole,chardev=mux0 \ > > -vnc 0.0.0.0:0 > > > > Which creates two backend devices: > > > > * Text virtual console (`vc0`) > > * A socket (`sock0`) connected to the single virtio hvc console with the > > help of the backend multiplexer (`mux0`) > > > > `vc0` renders text to an image, which can be shared over the VNC > protocol. > > `sock0` is a socket backend which provides bidirectional communication to > > the virtio hvc console. > > > > Once QEMU starts, the VNC client and any TTY emulator can be used to > > control a single hvc console. For example, these two different > > consoles should have similar input and output due to the buffer > > multiplexing: > > > > # VNC client > > vncviewer :0 > > > > # TTY emulator > > socat unix-connect:/tmp/sock pty,link=/tmp/pty > > tio /tmp/pty > > > > v4 .. v5: > > > > * Spelling fixes in qemu-options description > > * Memory leaks fixes in mux-be tests > > * Add sanity checks to chardev to avoid stacking of mux devices > > * Add corresponding unit test case to cover the creation of stacked > > muxers: `-chardev mux-be,mux-id-be=ID`, which is forbidden > > * Reflect the fact that stacking is not supported in the documentation > > > > v3 .. v4: > > > > * Rebase on latest chardev changes > > * Add unit tests which test corner cases: > > * Inability to remove mux with active frontend > > * Inability to add more chardevs to a mux than `MUX_MAX` > > * Inability to mix mux-fe and mux-be for the same chardev > > > > v2 .. v3: > > > > * Split frontend and backend multiplexer implementations and > > move them to separate files: char-mux-fe.c and char-mux-be.c > > > > v1 .. v2: > > > > * Separate type for the backend multiplexer `mux-be` > > * Handle EAGAIN on write to the backend device > > * Support of watch of previously failed backend device > > * Proper json support of the `mux-be-id` option > > * Unit test for the `mux-be` multiplexer > > > > [1] https://www.qemu.org/docs/master/system/qemu-manpage.html#hxtool-6 > > [2] https://github.com/lf-edge/eve > > > > Signed-off-by: Roman Penyaev <r.peni...@gmail.com> > > Cc: "Marc-André Lureau" <marcandre.lur...@redhat.com> > > Cc: qemu-devel@nongnu.org > > > > Roman Penyaev (8): > > chardev/char: rename `MuxChardev` struct to `MuxFeChardev` > > chardev/char: rename `char-mux.c` to `char-mux-fe.c` > > chardev/char: move away mux suspend/resume calls > > chardev/char: rename frontend mux calls > > chardev/char: introduce `mux-be-id=ID` option > > chardev/char-mux: implement backend chardev multiplexing > > tests/unit/test-char: add unit test for the `mux-be` multiplexer > > qemu-options.hx: describe multiplexing of several backend devices > > > > chardev/char-fe.c | 25 +- > > chardev/char-mux-be.c | 290 +++++++++++++++++++++++ > > chardev/{char-mux.c => char-mux-fe.c} | 157 ++++--------- > > chardev/char.c | 139 +++++++++-- > > chardev/chardev-internal.h | 55 ++++- > > chardev/meson.build | 3 +- > > include/chardev/char.h | 8 +- > > qapi/char.json | 31 ++- > > qemu-options.hx | 80 +++++-- > > system/vl.c | 4 +- > > tests/unit/test-char.c | 323 +++++++++++++++++++++++++- > > 11 files changed, 947 insertions(+), 168 deletions(-) > > create mode 100644 chardev/char-mux-be.c > > rename chardev/{char-mux.c => char-mux-fe.c} (71%) > > > > -- > > 2.34.1 > > > > -- Marc-André Lureau
