linux-kernel - Re: [PATCH v2 4/4] x86/static_call: Add inline static call implementation for x86-64

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Date:   Fri, 30 Nov 2018 22:13:42 +0100 (CET)
From:   Jiri Kosina <jikos@...nel.org>
To:     Andy Lutomirski <luto@...nel.org>
cc:     Steven Rostedt <rostedt@...dmis.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>, X86 ML <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Jason Baron <jbaron@...mai.com>,
        David Laight <David.Laight@...lab.com>,
        Borislav Petkov <bp@...en8.de>, julia@...com, jeyu@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v2 4/4] x86/static_call: Add inline static call implementation
 for x86-64

On Fri, 30 Nov 2018, Andy Lutomirski wrote:

> According to the SDM, you can program the APIC ICR to request an SMI. 
> It's not remotely clear to me what will happen if we do this.  

I think one of the known reliable ways to trigger SMI is to write 0x0 to 
the SMI command I/O port (0xb2).

> For all I know, the SMI handler will explode and the computer will catch 
> fire.

Ha, therefore noone can't claim any more that SMIs are always harmful :)

-- 
Jiri Kosina
SUSE Labs