| Message ID | 20241017144316.517709-1-r.peniaev@gmail.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | chardev: implement backend chardev multiplexing | expand |
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? -- Roman On Thu, Oct 17, 2024 at 4:45 PM Roman Penyaev <r.peniaev@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.peniaev@gmail.com> > Cc: "Marc-André Lureau" <marcandre.lureau@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 >
Hi Roman On Thu, Oct 31, 2024 at 3:12 PM Roman Penyaev <r.peniaev@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.peniaev@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.peniaev@gmail.com> > > Cc: "Marc-André Lureau" <marcandre.lureau@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 > > > >
On Thu, Oct 31, 2024 at 12:34 PM Marc-André Lureau <marcandre.lureau@gmail.com> wrote: > > Hi Roman > > On Thu, Oct 31, 2024 at 3:12 PM Roman Penyaev <r.peniaev@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. With CLI it seems not a problem: you can always use the ',,' sequence, or we can introduce another separator, for example ':'. With JSON I could not find a working array example, but probably the same trick with any separator in a string can work as well. What do you think? > I would like others to comment.. Probably makes sense to ping them once again. -- Roman
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.peniaev@gmail.com> Cc: "Marc-André Lureau" <marcandre.lureau@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%)