On Mon, May 18, 2020 at 1:03 AM Thomas Gleixner <t...@linutronix.de> wrote: > > Andy Lutomirski <l...@kernel.org> writes: > > On Sun, May 17, 2020 at 1:48 AM Thomas Gleixner <t...@linutronix.de> wrote: > >> Remember this is about ensuring that all the state is properly > >> established before any of this instrumentation muck can happen. > >> > >> DR7 handling is specific to #DB and done even before nmi_enter to > >> prevent recursion. > > > > So why is this change needed? > > We really want nmi_enter() to be the carefully crafted mechanism which > establishes correct state in whatever strange context the exception > hits. Not more, not less. > > Random instrumentation has absolutely no business there and I went a > long way to make sure that this is enforcible by objtool. > > Aside of that the tracing which is contained in nmi_enter() is about > taking timestamps for hardware latency detection. If someone runs > hardware latency detection with active break/watchpoints then I really > can't help it. >
Okay. I'll stop looking for the bug you're fixing, then.
