From: Peter Zijlstra <peterz@infradead.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Nikolay Borisov <nborisov@suse.com>,
LKML <linux-kernel@vger.kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
bpf@vger.kernel.org, Josh Poimboeuf <jpoimboe@redhat.com>
Subject: Re: kprobes broken since 0d00449c7a28 ("x86: Replace ist_enter() with nmi_enter()")
Date: Fri, 29 Jan 2021 17:24:38 +0100 [thread overview]
Message-ID: <20210129162438.GC8912@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20210129105952.74dc8464@gandalf.local.home>
On Fri, Jan 29, 2021 at 10:59:52AM -0500, Steven Rostedt wrote:
> On Fri, 29 Jan 2021 22:40:11 +0900
> Masami Hiramatsu <mhiramat@kernel.org> wrote:
>
> > > So what, they can all happen with random locks held. Marking them as NMI
> > > enables a whole bunch of sanity checks that are entirely appropriate.
> >
> > How about introducing an idea of Asynchronous NMI (ANMI) and Synchronous
> > NMI (SNMI)? kprobes and ftrace is synchronously called and can be controlled
> > (we can expect the context) but ANMI may be caused by asynchronous
> > hardware events on any context.
> >
> > If we can distinguish those 2 NMIs on preempt count, bpf people can easily
> > avoid the inevitable situation.
>
> I don't like the name NMI IN SNMI, because they are not NMIs. They are
> actually more like kernel exceptions. Even page faults in the kernel is
> similar to a kprobe breakpoint or ftrace. It can happen anywhere, with any
> lock held. Perhaps we need a kernel exception context? Which by definition
> is synchronous.
What problem are you trying to solve? AFAICT all these contexts have the
same restrictions, why try and muck about with different names for the
same thing?
next prev parent reply other threads:[~2021-01-29 16:33 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <25cd2608-03c2-94b8-7760-9de9935fde64@suse.com>
[not found] ` <20210128001353.66e7171b395473ef992d6991@kernel.org>
[not found] ` <20210128002452.a79714c236b69ab9acfa986c@kernel.org>
[not found] ` <a35a6f15-9ab1-917c-d443-23d3e78f2d73@suse.com>
[not found] ` <20210128103415.d90be51ec607bb6123b2843c@kernel.org>
2021-01-28 3:38 ` kprobes broken since 0d00449c7a28 ("x86: Replace ist_enter() with nmi_enter()") Masami Hiramatsu
2021-01-28 7:11 ` Nikolay Borisov
2021-01-28 16:12 ` Nikolay Borisov
2021-01-28 16:45 ` Nikolay Borisov
2021-01-28 16:50 ` Josh Poimboeuf
2021-01-28 21:52 ` [PATCH] x86: Disable CET instrumentation in the kernel Josh Poimboeuf
2021-01-29 6:23 ` Nikolay Borisov
2021-01-29 10:21 ` Borislav Petkov
[not found] ` <20210129151034.iba4eaa2fuxsipqa@treble>
2021-01-29 16:30 ` Borislav Petkov
2021-01-29 16:49 ` Josh Poimboeuf
2021-01-29 16:54 ` Nikolay Borisov
2021-01-29 17:03 ` Josh Poimboeuf
2021-01-29 17:07 ` Borislav Petkov
2021-01-29 17:58 ` Seth Forshee
2021-01-28 18:24 ` kprobes broken since 0d00449c7a28 ("x86: Replace ist_enter() with nmi_enter()") Peter Zijlstra
2021-01-29 1:34 ` Alexei Starovoitov
2021-01-29 6:36 ` Nikolay Borisov
[not found] ` <YBPNyRyrkzw2echi@hirez.programming.kicks-ass.net>
[not found] ` <20210129224011.81bcdb3eba1227c414e69e1f@kernel.org>
[not found] ` <20210129105952.74dc8464@gandalf.local.home>
2021-01-29 16:24 ` Peter Zijlstra [this message]
2021-01-29 17:45 ` Alexei Starovoitov
2021-01-29 17:59 ` Peter Zijlstra
2021-01-29 19:01 ` Steven Rostedt
2021-01-29 21:05 ` Alexei Starovoitov
2021-01-30 1:41 ` Masami Hiramatsu
2021-01-29 21:24 ` Steven Rostedt
2021-01-30 8:28 ` Peter Zijlstra
2021-01-30 12:44 ` Steven Rostedt
2021-02-02 10:45 ` Peter Zijlstra
2021-02-02 14:52 ` Steven Rostedt
2021-02-02 16:45 ` Peter Zijlstra
2021-02-02 16:56 ` Steven Rostedt
2021-02-02 18:30 ` Peter Zijlstra
2021-02-02 21:05 ` Steven Rostedt
2021-02-03 13:33 ` Masami Hiramatsu
2021-02-03 13:52 ` Steven Rostedt
2021-01-30 2:02 ` Masami Hiramatsu
2021-01-30 3:08 ` Alexei Starovoitov
2021-01-30 12:10 ` Masami Hiramatsu
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