Messages in this thread | | | Date | Wed, 26 Feb 2020 19:42:37 +0100 | From | Borislav Petkov <> | Subject | Re: [patch 02/10] x86/mce: Disable tracing and kprobes on do_machine_check() |
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On Wed, Feb 26, 2020 at 09:28:51AM -0800, Andy Lutomirski wrote: > > It entirely depends on what the goal is :-/ On the one hand I see why > > people might want function tracing / kprobes enabled, OTOH it's all > > mighty frigging scary. Any tracing/probing/whatever on an MCE has the > > potential to make a bad situation worse -- not unlike the same on #DF.
FWIW, I had this at the beginning of the #MC handler in a feeble attempt to poke at this:
+ hw_breakpoint_disable(); + static_key_disable(&__tracepoint_read_msr.key); + tracing_off();
But then Tony noted that some recoverable errors do get reported with an #MC exception so we would have to look at the error severity and then decide whether to allow tracing or not.
But the error severity happens all the way down in __mc_scan_banks() - i.e., we've executed the half handler already.
So, frankly, I wanna say, f*ck tracing etc - there are certain handlers which simply don't allow it. And we'll only consider changing that when a really good reason for it appears...
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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