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]
The serial-manager thread was the only VMM-managed thread without a
seccomp filter. Add a Thread::SerialManager variant and whitelist the
31 syscalls needed for its epoll-based I/O loop (read, write, socket
ops, signal handling, memory allocation, glibc internals).
The filter is computed in start_thread() and applied before the epoll
loop, matching the pattern used by other VMM threads.
Signed-off-by: Wei Liu <liuwe@microsoft.com>
Assisted-by: Pi-agent:Claude-Opus-4.7
It makes most sense to create the epoll FD and add the kill event before
identifying the transport specific fd.
Signed-off-by: Rob Bradford <rbradford@meta.com>
This is not just used for determine the output but also the input to the
console where this can be bidirectional.
Signed-off-by: Rob Bradford <rbradford@meta.com>
Fix the condition to correctly identify a new PTY connection.
Fixes: 287887c99 (vmm: fix console IO safety)
Signed-off-by: Praveen K Paladugu <prapal@linux.microsoft.com>
Previously, `into_raw_fd()` transferred fd ownership to epoll while
keeping separate clones in `reader` and `writer`, causing leaks when
the stream was closed. Now, `reader` owns the fd and epoll borrows it.
When the FD is closed in the kernel, reader will be reset to None.
Signed-off-by: Praveen K Paladugu <prapal@linux.microsoft.com>
Fix clippy warning `uninlined_format_args` reported by rustc rustc
1.89.0 (29483883e 2025-08-04).
```console
warning: variables can be used directly in the `format!` string
--> block/src/lib.rs:649:17
|
649 | info!("{} failed to create io_uring instance: {}", error_msg, e);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#uninlined_format_args
= note: `#[warn(clippy::uninlined_format_args)]` on by default
help: change this to
|
649 - info!("{} failed to create io_uring instance: {}", error_msg, e);
649 + info!("{error_msg} failed to create io_uring instance: {e}");
|
```
Signed-off-by: Ruoqing He <heruoqing@iscas.ac.cn>
The changes were mostly automatically applied using the following
Python script:
```python
import os, re
for root, _, files in os.walk("."):
for f in files:
if not f.endswith(".rs"):
continue
p = os.path.join(root, f)
with open(p, "r", encoding="utf-8") as file:
lines = file.readlines()
changed = False
for i in range(len(lines) - 1):
if re.search(r'#\[error\(".*: \{0[^}]*\}"\)\]', lines[i]) and "#[source]" in lines[i + 1].strip():
lines[i] = re.sub(r': \{0[^}]*\}"\)\]', '")]', lines[i])
changed = True
if changed:
with open(p, "w", encoding="utf-8") as file:
file.writelines(lines)
print("Fixed:", p)
```
Signed-off-by: Philipp Schuster <philipp.schuster@cyberus-technology.de>
On-behalf-of: SAP philipp.schuster@sap.com
# Conflicts:
# vmm/src/api/http/mod.rs
Historically the Cloud Hypervisor coding style has been to ensure that
all imports are ordered and placed in a single group. Unfortunately
cargo fmt has no support for ensuring that all imports are in a single
group so if whitespace lines were added as part of the import statements
then they would only be odered correctly in the group.
By adopting "group_imports="StdExternalCrate" we can enforce a style
where imports are placed in at most three groups for std, external
crates and the crate itself. Choosing a style enforceable by the tooling
reduces the reviewer burden.
Signed-off-by: Rob Bradford <rbradford@rivosinc.com>
Rebooting a VM fails with the following error when debug assertions
are enabled:
fatal runtime error: IO Safety violation: owned file descriptor already closed
This happens because FromRawFd::from_raw_fd is used on RawFds stored
in ConsoleInfo every time a VM begins to boot, so the second
time (after a reboot, or if the first attempt to boot via the API
failed), the fd will be closed. Until this assertion is hit, the code
is operating on either closed file descriptors, or new file
descriptors for something completely different. If debug assertions
are disabled, it will just continue doing this with unpredictable
results.
To fix this, and prevent the problem reocurring, ownership of the
console file descriptors needs to be properly tracked, using Rust's
type system, so this commit refactors the console code to do that.
The file descriptors are now passed around with reference counts, so
they won't be closed prematurely. The obvious way to do this would be
to just have each member of ConsoleInfo be an Arc<File>, but we need
to accomodate that serial console file descriptors can also be
sockets. We can't just store an OwnedFd and convert it when it's
used, because we only get a reference from the Arc, so we need to
store the descriptors as their concrete types in an enum. Since this
basically duplicates the ConsoleOutputMode enum from the config, the
ConsoleOutputMode enum is now not used past constructing the
ConsoleInfo.
So that ownership can be represented consistently, the debug console's
tty mode now uses its own stdout descriptor.
I'm still using .try_clone().unwrap() (i.e. dup()) to clone file
descriptors for Endpoint::FilePair and Endpoint::TtyPair, because I
assume there's a reason for them not just to hold a single file
descriptor.
I've also retained the existing behaviour of having serial manager
ignore the tty file descriptor passed to it (which is stdout), and
instead using stdin. It looks a lot weirder now, because it has to
explicitly indicate it's ignoring the fd with an underscore binding.
Fixes: 52eebaf6 ("vmm: refactor DeviceManager to use console_info")
Signed-off-by: Alyssa Ross <hi@alyssa.is>
I've moved this so that it's just after the enum definition, which
will hopefully make it less easy to miss if events are added/removed
again in future.
Fixes: 6d1077fc ("vmm: Unix socket backend for serial port")
Signed-off-by: Alyssa Ross <hi@alyssa.is>
While adding console devices, DeviceManager will now use the FDs in
console_info instead of creating them.
To reduce the size of this commit, I marked some variables are unused
with '_' prefix. All those variables are cleaned up in next commit.
Signed-off-by: Praveen K Paladugu <prapal@linux.microsoft.com>
The original code gave an owned fd to UnixListener. That made the same
fd wrapped into two owned files.
When the files were dropped, the same fd would be closed more than once.
A newly introduced check in Rust's stdlib caught that error.
A newly cloned fd should be given to UnixListener.
Fixes: #6485
Signed-off-by: Wei Liu <liuwe@microsoft.com>
Cloud-Hypervisor takes a path for Unix socket, where it will listen
on. Users can connect to the other end of the socket and access serial
port on the guest.
"--serial socket=/path/to/socket" is the cmdline option to pass to
cloud-hypervisor.
Users can use socat like below to access guest's serial port once the
guest starts to boot:
socat -,crnl UNIX-CONNECT:/path/to/socket
Signed-off-by: Praveen K Paladugu <prapal@linux.microsoft.com>
warning: useless use of `vec!`
--> test_infra/src/lib.rs:111:30
|
111 | let mut events = vec![epoll::Event::new(epoll::Events::empty(), 0); 1];
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: you can use an array directly: `[epoll::Event::new(epoll::Events::empty(), 0); 1]`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#useless_vec
= note: `#[warn(clippy::useless_vec)]` on by default
Signed-off-by: Yu Li <liyu.yukiteru@bytedance.com>
To align the logging messages with the rest of the code, this
message should be aligned with another similar occurrence in
epoll_helper.rs
Signed-off-by: Philipp Schuster <philipp.schuster@cyberus-technology.de>
We want to be able to reuse the SerialBuffer from the virtio-devices
crate, particularly from the virtio-console implementation. That's why
we move the SerialBuffer definition to its own crate so that it can be
accessed from both vmm and virtio-devices crates, without creating any
cyclic dependency.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
If the epoll_wait() call returns EINTR, this only means a signal has
been delivered before any of the file descriptors registered triggered
an event or before the end of the timeout (if timeout isn't -1). For
that reason, we should simply try to listen on the epoll loop again.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
The goal of this patch is to provide a reliable way to detect when the
other end of the PTY is connected, and therefore be able to identify
when we can write to the PTY device. This is needed because writing to
the PTY device when the other end isn't connected causes the loss of
the written bytes.
The way to detect the connection on the other end of the PTY is by
knowing the other end is disconnected at first with the presence of the
EPOLLHUP event. Later on, when the connection happens, EPOLLHUP is not
triggered anymore, and that's when we can assume it's okay to write to
the PTY main device.
It's important to note we had to ensure the file descriptor for the
other end was closed, otherwise we would have never seen the EPOLLHUP
event. And we did so by removing the "sub" field from the PtyPair
structure as it was keeping the associated File opened.
Fixes#3170
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Refactor the serial buffer handling in order to write the serial
buffer's output to a PTY connected after the serial device stops being
written to by the guest.
This change moves the serial buffer initialization inside the serial
manager. That is done to allow the serial buffer to be made aware of
the PTY and epoll fds needed in order to modify the
EpollDispatch::File trigger. These are then used by the serial buffer
to trigger an epoll event when the PTY fd is writable and the buffer
has content in it. They are also used to remove the trigger when the
buffer is emptied in order to avoid unnecessary wake-ups.
Signed-off-by: William Douglas <william.douglas@intel.com>
This change adds a SerialManager with its own epoll handling that
should be created and run by the DeviceManager when creating an
appropriately configured console (serial tty or pty).
Both stdin and pty input are handled by the SerialManager. The stdin
and pty specific methods used by the VMM should be removed in a future
commit.
Signed-off-by: William Douglas <william.douglas@intel.com>
