From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 23305C34049 for ; Tue, 18 Feb 2020 20:53:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EFCEE206F4 for ; Tue, 18 Feb 2020 20:53:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="kg8vaZSx" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726717AbgBRUxF (ORCPT ); Tue, 18 Feb 2020 15:53:05 -0500 Received: from mail.skyhub.de ([5.9.137.197]:34584 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726652AbgBRUxE (ORCPT ); Tue, 18 Feb 2020 15:53:04 -0500 Received: from zn.tnic (p200300EC2F0C1F00DCB96C3517B36067.dip0.t-ipconnect.de [IPv6:2003:ec:2f0c:1f00:dcb9:6c35:17b3:6067]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id A19A21EC0CC5; Tue, 18 Feb 2020 21:53:03 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1582059183; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=vu8m624OFoj255XrypvCF+xJOrys4/F45UEHhTG4GXs=; b=kg8vaZSxwLoVAJBvvKk9xY1hv8V1IMZkOGiGimHRhIEuMxeqwUPFaBLM96duBzCAyBgaDK p0upM+YjaIQAPp/PP4JUIdW1A6EP638LU/j1FaIH3Um/O9RQz2iGWb5vEIe4SrinIHsz0V 06H7isQ1cRLE5obqxjypCQqmiMCTnM0= Date: Tue, 18 Feb 2020 21:52:24 +0100 From: Borislav Petkov To: Steven Rostedt Cc: Peter Zijlstra , Andy Lutomirski , Tony Luck , x86-ml , lkml Subject: Re: [RFC] #MC mess Message-ID: <20200218205224.GT14449@zn.tnic> References: <20200218173150.GK14449@zn.tnic> <20200218131158.693eeefc@gandalf.local.home> <20200218195035.GN14449@zn.tnic> <20200218150850.224d9b8e@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200218150850.224d9b8e@gandalf.local.home> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 18, 2020 at 03:08:50PM -0500, Steven Rostedt wrote: > You could have the msr_tracepoint_active() check this per cpu variable? > > msr reading and writing is rather slow, and I'm sure reading a per_cpu > variable is going to be in the noise of it. Yeah, I was worrying about using the tracing MSR variants in NMI context but Peter says tracing should do in_nmi() if it isn't doing so. Same with #MC: we hold a subsequent #MC from getting raised with MCIP - thanks Tony - but we can have other exceptions raised while in the #MC handler. That too should be taken care of with the in_nmi() thing. Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette