Re: [PATCH v2] reboot: allow to specify reboot mode via sysfs

[Matteo Croce]

On Fri, Nov 6, 2020 at 11:33 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> On Fri,  6 Nov 2020 21:07:04 +0100 Matteo Croce <mcroce@xxxxxxxxxxxxxxxxxxx> wrote:
>
> > The kernel cmdline reboot= option offers some sort of control
> > on how the reboot is issued.
> > Add handles in sysfs to allow setting these reboot options, so they
> > can be changed when the system is booted, other than at boot time.
>
> Please include a description of why you believe the kernel needs this
> feature.  Use cases, end-user benefits, etc.
>
> We've survived this long without it - what changed?

Hi Andrew,

We don't always know in advance what type of reboot to perform.

Sometimes a warm reboot is preferred to persist certain memory regions
across the reboot. Others a cold one is needed to apply a future system
update that makes a memory memory model change, like changing the base
page size or resizing a persistent memory region.

Or simply we want to enable reboot_force because we noticed that
something bad happened.

Bye,
-- 
per aspera ad upstream