Re: [PATCH v1 1/3] liveupdate: skip serialization for context-preserving kexec

[Pasha Tatashin <pasha.tatashin@soleen.com>]

On 05-06 17:33, Pratyush Yadav wrote:
> On Wed, May 06 2026, Pasha Tatashin wrote:
> 
> > On 05-06 10:31, Pratyush Yadav wrote:
> >> Hi Pasha,
> >> 
> >> On Wed, May 06 2026, Pasha Tatashin wrote:
> >> 
> >> > A preserve_context kexec returns to the current kernel, which
> >> > is unrelated to live update where the state is passed to the next
> >> > kernel. Skip liveupdate_reboot() in this case to avoid serialization
> >> > and prevent sessions from being left in a frozen state upon return.
> >> 
> >> Should we also stop KHO? Now it is stateless and always finalized. I am
> >
> > No. KHO preserves kernel internal memory; for context-preserved 
> > kexec, the 2nd kernel and the 1st kernel do not have overlapping 
> > memory. So, whatever the 1st kernel maintains in KHO is an internal 
> > detail of the 1st kernel. Once we return from the 2nd kernel to the 1st 
> > kernel, all KHO memory is going to stay as-is, and the 1st kernel can 
> > even perform a regular kexec or live update later.
> 
> My point is that we keep KHO data in the 1st kernel but do not pass it
> to the 2nd kernel via setup_data or the devicetree because it should not
> use that memory anyway. So essentially we add a check in
> kho_fill_kimage() and return early if preserve_context is set.

This is a good point, I think we should do that to prevent passing via 
setup_data on preserve_context kexec.

> 
> I don't think it makes much difference in practice so no strong
> opinions. Fine either way.
> 
> [...]
> 
> -- 
> Regards,
> Pratyush Yadav