[PATCH v4 4/5] kexec: add option to fall back to KEXEC_LOAD when KEXEC_FILE_LOAD is not supported.

[Michal Suchánek]

On Fri, 16 Mar 2018 14:45:02 +0800
Dave Young <dyoung at redhat.com> wrote:

> On 03/15/18 at 12:06pm, Michal Suchánek wrote:
> > On Wed, 14 Mar 2018 11:21:59 +0800
> > Dave Young <dyoung at redhat.com> wrote:
> >   
> > > It looks to me it is enough only checking -ENOSYS maybe also
> > > -ENOTSUPP and then set do_kexec_file_syscall = 0;
> > > 
> > > EINVAL and ENOEXEC are real errors, I do not understand why still 
> > > fallback.    
> > 
> > If you pass an image type that the kernel does not understand (eg.
> > multiboot or uImage) then the kernel will return a real error
> > because it does not understand the image. However, kexec-tools
> > should still be able to load it, automatically. That's what the
> > -auto stands for.  
> 
> This semes over engineering, the initial purpose is to fallback when
> kexec_file_load is not supported, so I would suggest not to do more
> than that.

The initial purpose is for users to not need to specify any flag to
select a syscall to use. Since this is not acceptable because it might
make kexec work out of the box on systems where it was previously broken
or whatever this new flag is supposed to achieve that: when specified
kexec tries hard to do the best thing possible with the image it
received.

Thanks

Michal