Re: [PATCH v4] kho: kexec-metadata: track previous kernel chain

Breno Leitao
2026-01-26T10:52:28Z

On Sun, Jan 25, 2026 at 01:32:27PM +0200, Mike Rapoport wrote:
> On Thu, Jan 22, 2026 at 04:04:55AM -0800, Breno Leitao wrote:
> > Ack! I am planning something as:
> >
> > commit 90e098ca0d611b44594f08e50ba1cff3c932dd2b
> > Author: Breno Leitao <leitao@debian.org>
> > Date: Thu Jan 22 03:47:23 2026 -0800
> >
> > kho: document kexec-metadata tracking feature

...

> I'd move this section before "debugfs Interfaces", other than that LGTM.

Ack!

> > > Can't we move it into the existing if (fdt) below?
> >
> > Unfortunately, that won't work due to a data dependency between the two
> > functions.
> >
> > kho_process_kexec_metadata() reads from the FDT subtree and populates kho_in:
> >
> > Basically:
> >
> > kho_in.kexec_count = metadata->kexec_count;
> >
> > While kho_populate_kexec_metadata() increments metadata->kexec_count:
> >
> > /* kho_in.kexec_count is set to 0 on cold boot */
> > metadata->kexec_count = kho_in.kexec_count + 1;
> >
> > If kho_process_kexec_metadata() is moved after kho_populate_kexec_metadata(),
> > the count would always increment from 0 to 1, ignoring whatever was passed in
> > the FDT.
> >
> > Restructuring to call kho_in_debugfs_init() earlier also doesn't work:
> >
> >
> > if (fdt) {
> > kho_in_debugfs_init(&kho_in.dbg, fdt);
> > kho_process_kexec_metadata();
> > return 0;
> > }
> >
> > /* Populate kexec metadata for the possible next kexec */
> > err = kho_populate_kexec_metadata();
> > if (err)
> > pr_warn("failed to initialize kexec-metadata subtree: %d\n",
> > err);
> >
> > This would return early without populating the kexec metadata for the next
> > kexec, breaking the chain on KHO boots.
>
> How about we rename kho_process_kexec_metadata() to
> kho_retreive_kexec_metadata() and add kho_process_kexec_metadata() that
> will first call _retrieve and then _populate? Something like
>
> static int __init kho_process_kexec_metadata(const void *fdt)
> {
> int err;
>
> if (fdt)
> kho_retrieve_kexec_metadata();
>
> /* Populate kexec metadata for the possible next kexec */
> err = kho_populate_kexec_metadata();
> if (err)
> pr_warn("failed to initialize kexec-metadata subtree: %d\n",
> err);
>
> return err;
> }

That would work, I will probably rename it to kho_kexec_metadata_init()
or kho_kexec_metadata_setup() to follow the same pattern already there.

Thanks for the review, I will send an updated version soon,
--breno