mbox series

[SRU,G/aws,0/1] fix broken /dev/console on i3.metal

Message ID 20200924105321.283171-1-andrea.righi@canonical.com
Headers show
Series fix broken /dev/console on i3.metal | expand

Message

Andrea Righi Sept. 24, 2020, 10:53 a.m. UTC 
BugLink: https://bugs.launchpad.net/bugs/1896604

[Impact]

Starting with kernel 5.8 the default nr_uarts has been changed from 4 to
2 for amd64, but this seems to affect i3.metal instances in AWS, because
ttyS0 is now remapped to ttyS4 and this is breaking tools like
cloud-init (and probably something else).

[Test case]

# echo > /dev/console
bash: echo: write error: Input/output error

[Fix]

Setting nr_uarts=4 by default (via CONFIG_SERIAL_8250_RUNTIME_UARTS)
restores the previous behavior and writing to /dev/console works without
returning any error.

[Regression potential]

Minimal. Restores the old behavior used in 5.4 (that shouldn't have
changed in the first place).

Comments

Colin Ian King Sept. 24, 2020, 10:55 a.m. UTC | #1 
On 24/09/2020 11:53, Andrea Righi wrote:
> BugLink: https://bugs.launchpad.net/bugs/1896604
> 
> [Impact]
> 
> Starting with kernel 5.8 the default nr_uarts has been changed from 4 to
> 2 for amd64, but this seems to affect i3.metal instances in AWS, because
> ttyS0 is now remapped to ttyS4 and this is breaking tools like
> cloud-init (and probably something else).
> 
> [Test case]
> 
> # echo > /dev/console
> bash: echo: write error: Input/output error
> 
> [Fix]
> 
> Setting nr_uarts=4 by default (via CONFIG_SERIAL_8250_RUNTIME_UARTS)
> restores the previous behavior and writing to /dev/console works without
> returning any error.
> 
> [Regression potential]
> 
> Minimal. Restores the old behavior used in 5.4 (that shouldn't have
> changed in the first place).
> 
> 
Makes perfect sense, hard to see any real regression potential here.
Thanks Andrea.

Acked-by: Colin Ian King <colin.king@canonical.com>
Andrea Righi Sept. 24, 2020, 11:13 a.m. UTC | #2 
On 24/09/2020 11:53, Andrea Righi wrote:
> BugLink: https://bugs.launchpad.net/bugs/1896604
> 
> [Impact]
> 
> Starting with kernel 5.8 the default nr_uarts has been changed from 4 to
> 2 for amd64, but this seems to affect i3.metal instances in AWS, because
> ttyS0 is now remapped to ttyS4 and this is breaking tools like
> cloud-init (and probably something else).
> 
> [Test case]
> 
> # echo > /dev/console
> bash: echo: write error: Input/output error
> 
> [Fix]
> 
> Setting nr_uarts=4 by default (via CONFIG_SERIAL_8250_RUNTIME_UARTS)
> restores the previous behavior and writing to /dev/console works without
> returning any error.
> 
> [Regression potential]
> 
> Minimal. Restores the old behavior used in 5.4 (that shouldn't have
> changed in the first place).