[PATCH] kexec: Add --lite option

[Geoff Levand]

Hi Dave,

On Thu, 2015-10-22 at 11:17 +0800, Dave Young wrote:
> On 10/21/15 at 04:12pm, Geoff Levand wrote:
> > Add a new option --lite to kexec that allows for a fast reboot
> > by avoiding the purgatory integrity checks.  This option is
> > intended for use by kexec based bootloaders that load a new
> > image and then immediately transfer control to it.
> 
> I think Vivek was rejecting this --lite since kdump need the purgatory
> integrity checks. Ccing him.

As stated, this is not intended for use by kdump.

This is an optional feature.  It does not remove the integrity
checks, but provides the user a way to bypass them if they so
desire.

> > It was reported that on some systems where purgatory is running
> > without caches enabled the sha256 calculations would take several
> > minutes.  For bootloaders that just load a new image and
> > immediately jump into it the loss of the integrity check is worth
> > the increase in boot speed.  Please consider.  
> 
> Pratyush reported the arm64 issue, he sent a patch to fix it with
> enabling cache for purgatory. I think the patch can fix the problem.
> Why not fix it? The fix is simple enough and it does not introduce
> complicate logic.

This patch also is simple, and is architecture independent.  I see this
feature as an improvement to kexec, not necessarily as a fix for that
problem.

-Geoff