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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 9B6DEC43381 for ; Tue, 19 Feb 2019 09:19:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 69A7221904 for ; Tue, 19 Feb 2019 09:19:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="ZeErcinx" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727986AbfBSJTc (ORCPT ); Tue, 19 Feb 2019 04:19:32 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:40274 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727250AbfBSJTc (ORCPT ); Tue, 19 Feb 2019 04:19:32 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=RroBk7fs8CRSGgKhBmgKC8IAco1Oh6TluQO/2qsXZhQ=; b=ZeErcinxMR3VEEs6ZftOlGMq8 zXsJj7oL1hDokgePdwx7STlW7b5DrRWJjmdf3nK0XTIxcv0830ndu+GW2kDM6EMRwEjlagH+Fz3hd i/ZskpQf8nfFyIoBFKVaUY0l4+Mh/NJR5hAAOB6PhbQYBPdCisqT/lThCEo2UMQeGQXKRzhC2+SHa zdlWeR2ETVJah6mEXwELCxuc7vgsBRzXgMXZqY7QebTF1azuuXMrmCOe56N/jY1fNkIxruvfhkbqY +viQH1n5aIC9v/WunW+ALkx42h9hkwswhEk2bo1ZDdPr6Ylwi+HVGrwpIbpee/4m0HFMBXGv6wTNO 1Rx8AEsrQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1gw1Yk-0000Cr-NP; Tue, 19 Feb 2019 09:19:26 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 3FF71286C98E1; Tue, 19 Feb 2019 10:19:25 +0100 (CET) Date: Tue, 19 Feb 2019 10:19:25 +0100 From: Peter Zijlstra To: Linus Torvalds Cc: "H. Peter Anvin" , Andy Lutomirski , Julien Thierry , Will Deacon , Ingo Molnar , Linux List Kernel Mailing , "linux-alpha@vger.kernel.org" , Ingo Molnar , Catalin Marinas , James Morse , valentin.schneider@arm.com, Brian Gerst , Josh Poimboeuf , Andrew Lutomirski , Borislav Petkov , Denys Vlasenko , Thomas Gleixner Subject: Re: [PATCH] sched/x86: Save [ER]FLAGS on context switch Message-ID: <20190219091925.GU32534@hirez.programming.kicks-ass.net> References: <20190213154532.GQ32534@hirez.programming.kicks-ass.net> <20190213222146.GC32494@hirez.programming.kicks-ass.net> <20190214101429.GD32494@hirez.programming.kicks-ass.net> <20ABBED1-E505-45F6-8520-FB93786DF9A9@zytor.com> <20190216103044.GR32494@hirez.programming.kicks-ass.net> <9e037d68-75e7-1beb-0c9c-33a7ffeced1b@zytor.com> <20190219091525.GX32494@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190219091525.GX32494@hirez.programming.kicks-ass.net> 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 19, 2019 at 10:15:25AM +0100, Peter Zijlstra wrote: > On Mon, Feb 18, 2019 at 04:24:30PM -0800, Linus Torvalds wrote: > > On Mon, Feb 18, 2019 at 2:31 PM H. Peter Anvin wrote: > > > > > > The question is what "fix it" means. I'm really concerned about AC escapes, > > > and everyone else should be, too. > > > > I do think that it might be the right thing to do to add some kind of > > WARN_ON_ONCE() for AC being set in various can-reschedule situations. > > So I disagree. > > Either we set AC with preempt disabled, and then we don't need an extra > warning, because we already have a warning about scheduling with > preemption disabled, or we accept that the fault handler can run. n/m about the faults, forgot the obvious :/ I still really dislike wrecking the preemption model over this.