Re: [patch 02/10] x86/mce: Disable tracing and kprobes on do_machine_check()

Andy Lutomirski
2020-02-26T19:09:08Z

> On Feb 26, 2020, at 10:59 AM, Peter Zijlstra <peterz@infradead.org> wrote:
>
> ﻿On Wed, Feb 26, 2020 at 07:42:37PM +0100, Borislav Petkov wrote:
>> 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();
>
> You can't do static_key_disable() from an IST

Can we set a percpu variable saying “in some stupid context, don’t trace”?