[PATCH net-next 0/2] net: netconsole: convert to NBCON console infrastructure

[Breno Leitao <leitao@debian.org>]

This series adds support for the nbcon (new buffer console) infrastructure
to netconsole, enabling lock-free, priority-based console operations that
are safer in crash scenarios.

The implementation is introduced in three steps:

1) Refactor the message fragmentation logic into a reusable helper function
2) Extend nbcon support to non-extended (basic) consoles using the same
infrastructure.

The initial discussion about it appeared a while ago in [1], in order to
solve Mike's HARDIRQ-safe -> HARDIRQ-unsafe lock order warning, and the root
cause is that some hosts were calling IRQ unsafe locks from inside console
lock.

At that time, we didn't have the CON_NBCON_ATOMIC_UNSAFE yet. John
kindly implemented CON_NBCON_ATOMIC_UNSAFE in 187de7c212e5 ("printk:
nbcon: Allow unsafe write_atomic() for panic"), and now we can
implement netconsole on top of nbcon.

Important to note that netconsole continues to call netpoll and the
network TX helpers with interrupt disable, given the TX are called with
target_list_lock.

Link:
https://lore.kernel.org/all/b2qps3uywhmjaym4mht2wpxul4yqtuuayeoq4iv4k3zf5wdgh3@tocu6c7mj4lt/
[1]

Signed-off-by: Breno Leitao <leitao@debian.org>

Changes from RFC:
  * Removed the extra CONFIG for NBCON, given we don't want to support
    both console. Move to nbcon as the only console framework supported
  * Incorporated the changes from Petr.
  * Some renames to make the code more consistent.
  * Link: https://lore.kernel.org/all/20251121-nbcon-v1-0-503d17b2b4af@debian.org/

---
Breno Leitao (2):
      netconsole: extract message fragmentation into send_msg_udp()
      netconsole: convert to NBCON console infrastructure

 drivers/net/netconsole.c | 109 +++++++++++++++++++++++++++++------------------
 1 file changed, 68 insertions(+), 41 deletions(-)
---
base-commit: 7b8e9264f55a9c320f398e337d215e68cca50131
change-id: 20251117-nbcon-f24477ca9f3e

Best regards,
--  
Breno Leitao <leitao@debian.org>