On Mon 2026-05-18 14:25:04, Song Liu wrote:
> On Wed, May 13, 2026 at 7:34 AM Yafang Shao <[email protected]> wrote:
> >
> > Convert the replace attribute from a boolean to a u32 to function as a
> > "replace set." A newly loaded livepatch will now atomically replace
> > existing patches that belong to the same set.
> >
> > This change currently supports function replacement only; support for
> > state and shadow variables will be introduced in subsequent patches.
> >
> > Suggested-by: Song Liu <[email protected]>
> > Signed-off-by: Yafang Shao <[email protected]>
> > ---
> > .../livepatch/cumulative-patches.rst | 17 ++++++++------
> > Documentation/livepatch/livepatch.rst | 23 +++++++++++--------
> > include/linux/livepatch.h | 5 ++--
> > kernel/livepatch/core.c | 16 ++++++++-----
> > kernel/livepatch/state.c | 17 +++++++-------
> > kernel/livepatch/transition.c | 10 ++++----
> > scripts/livepatch/init.c | 7 +-----
> > scripts/livepatch/klp-build | 14 +++++------
> > 8 files changed, 59 insertions(+), 50 deletions(-)
> >
> > diff --git a/Documentation/livepatch/cumulative-patches.rst
> > b/Documentation/livepatch/cumulative-patches.rst
> > index 1931f318976a..6ef49748110e 100644
> > --- a/Documentation/livepatch/cumulative-patches.rst
> > +++ b/Documentation/livepatch/cumulative-patches.rst
> > @@ -17,18 +17,20 @@ from all older livepatches and completely replace them
> > in one transition.
> > Usage
> > -----
> >
> > -The atomic replace can be enabled by setting "replace" flag in struct
> > klp_patch,
> > -for example::
> > +The "replace_set" attribute in ``struct klp_patch`` acts as a **replace
> > set**,
> > +defining the scope of the replacement. By default, the replace set is 1.
> > +
> > +For example::
> >
> > static struct klp_patch patch = {
> > .mod = THIS_MODULE,
> > .objs = objs,
> > - .replace = true,
> > + .replace_set = 1,
> > };
>
> I wonder whether we should have "replace_set = 0" means no replace.
> This will simplify the transition for users of the existing replace=false
> option. I would like to hear other folks' thoughts on this.
I would find this confusing. Also it would complicate the code.
I always considered the "replace" and "no replace" mode as two
separate worlds:
+ people using many "no replace" livepatches
+ people always using atomic replace
But the code had to handle also the world where:
+ people might combine "no replace" and "replace all" livepatches
which looked like a clash of the two worlds. And different people might
have different expectations about the behavior.
The "replace_set" allows to remove this clash. It looks like a win-win.
And it makes the change acceptable for me.
Best Regards,
Petr
