cumulative patch and klp_patch->replace

[liu-song-6]

Hi,

I am building a live patch management framework.
Based on my understanding and experience, cumulative patch would simplify the work and is highly recommended. From kernel livepatch interface, klp_patch->replace can be used to do atomic switch from older version of patches to newer version. However, IIUC, kpatch does not use the replace flag. I wonder whether this is a design choice, or there is work in progress. I think the replace flag is still useful in some cases.

Thanks,
Song

[liu-song-6]

After some more thoughts, I think the replace feature will still be useful. So I created pull request #1183.

Thanks,
Song

[joe-lawrence]

Hi Song,

Good question. For us at Red Hat, I don't think we've been in a hurry to add atomic replace support to kpatch since we are still building and supporting older rhel-7 kpatches where atomic replace isn't supported. That said, I think it would be good for kpatch-build to support newer kernel features like this. Another one that comes to mind is the livepatch system state API.

For coding specifics, I'll add notes in a review for PR #1183

[joe-lawrence]

Implemented (thanks @liu-song-6 !) by: #1205 and #1183
Tagged in v0.9.4 by: #1215