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Message-ID: <20190418135858.n3lzq2oxkj52m6bi@treble> Date: Thu, 18 Apr 2019 08:58:58 -0500 From: Josh Poimboeuf <jpoimboe@...hat.com> To: Petr Mladek <pmladek@...e.com> Cc: Jiri Kosina <jikos@...nel.org>, Miroslav Benes <mbenes@...e.cz>, Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>, Joe Lawrence <joe.lawrence@...hat.com>, live-patching@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] livepatch: Convert error about unsupported reliable stacktrace into a warning On Thu, Apr 18, 2019 at 01:29:36PM +0200, Petr Mladek wrote: > The commit d0807da78e11d46f ("livepatch: Remove immediate feature") caused > that any livepatch was refused when reliable stacktraces were not supported > on the given architecture. > > The limitation is too strong. User space processes are safely migrated > even when entering or leaving the kernel. Kthreads transition would > need to get forced. But it is safe when: > > + The livepatch does not change the semantic of the code. > + Callbacks do not depend on a safely finished transition. > > Suggested-by: Josh Poimboeuf <jpoimboe@...hat.com> > Signed-off-by: Petr Mladek <pmladek@...e.com> > --- > kernel/livepatch/core.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c > index eb0ee10a1981..14f33ab6c583 100644 > --- a/kernel/livepatch/core.c > +++ b/kernel/livepatch/core.c > @@ -1003,11 +1003,10 @@ int klp_enable_patch(struct klp_patch *patch) > return -ENODEV; > > if (!klp_have_reliable_stack()) { > - pr_err("This architecture doesn't have support for the livepatch consistency model.\n"); > - return -EOPNOTSUPP; > + pr_warn("This architecture doesn't have support for the livepatch consistency model.\n"); > + pr_warn("The livepatch transition may never complete.\n"); > } > > - > mutex_lock(&klp_mutex); > > ret = klp_init_patch_early(patch); Thanks Petr. I would also suggest that we remove the WARN_ONCE() from the weak version of save_stack_trace_tsk_reliable(), since we expect it to be used in this case. -- Josh
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