Max Makarov 9889f6d403 vmm: buffer socket serial output for late-connecting clients ...

In Socket serial mode the device output sink was only installed once a
client connected, so output produced beforehand (kernel boot messages,
cloud-init) was dropped, and a client attaching after boot saw a blank
screen. Only PTY mode wrapped the sink in a SerialBuffer.

Install a persistent SerialBuffer as the Socket device's output sink at
SerialManager construction (discarding downstream via io::sink() until a
client connects), so output is captured into the 1 MiB ring even with no
client attached. On connect, retarget the buffer at the accepted client
and flush the backlog before live output resumes; on disconnect, keep
buffering so output produced while no client is attached is delivered to
the next one. The accepted socket is made non-blocking via
set_nonblocking() so a slow client cannot stall the vCPU thread
(SerialBuffer re-buffers on WouldBlock).

The serial-manager thread gains two syscalls under seccomp: sendto
(replaying the backlog is the first time it writes to the socket) and
ioctl restricted to FIONBIO, which is what set_nonblocking() issues.

Fixes: #7907

Signed-off-by: Max Makarov <maxpain@linux.com>
Assisted-by: Claude:claude-opus-4-8 [Claude Code]

2026-06-08 10:21:04 +00:00

..

src

vmm: buffer socket serial output for late-connecting clients

2026-06-08 10:21:04 +00:00

build.rs

build: Add "fuzzing" as a valid cfg(..) attribute

2024-05-08 08:10:28 +00:00

Cargo.toml

vmm: omit unset Option fields from API responses

2026-06-03 15:47:38 +01:00