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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 02D21C47254 for ; Tue, 5 May 2020 21:51:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C749B24963 for ; Tue, 5 May 2020 21:51:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729328AbgEEVvM (ORCPT ); Tue, 5 May 2020 17:51:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35878 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728737AbgEEVvM (ORCPT ); Tue, 5 May 2020 17:51:12 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 35823C061A0F for ; Tue, 5 May 2020 14:51:12 -0700 (PDT) Received: from p5de0bf0b.dip0.t-ipconnect.de ([93.224.191.11] helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1jW5ST-0005im-T7; Tue, 05 May 2020 23:50:34 +0200 Received: by nanos.tec.linutronix.de (Postfix, from userid 1000) id 5F06E1001F5; Tue, 5 May 2020 23:50:33 +0200 (CEST) From: Thomas Gleixner To: paulmck@kernel.org Cc: LKML , x86@kernel.org, Andy Lutomirski , Alexandre Chartre , Frederic Weisbecker , Paolo Bonzini , Sean Christopherson , Masami Hiramatsu , Petr Mladek , Steven Rostedt , Joel Fernandes , Boris Ostrovsky , Juergen Gross , Brian Gerst , Mathieu Desnoyers , Josh Poimboeuf , Will Deacon Subject: Re: [patch V4 part 1 12/36] x86/kvm: Sanitize kvm_async_pf_task_wait() In-Reply-To: <20200505175412.GG2869@paulmck-ThinkPad-P72> References: <20200505131602.633487962@linutronix.de> <20200505134059.262701431@linutronix.de> <20200505175412.GG2869@paulmck-ThinkPad-P72> Date: Tue, 05 May 2020 23:50:33 +0200 Message-ID: <87368erqza.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org "Paul E. McKenney" writes: > On Tue, May 05, 2020 at 03:16:14PM +0200, Thomas Gleixner wrote: >> RCU is watching for: >> >> #1 The vCPU exited and current is definitely not the idle task >> >> #2a The #PF entry code on the guest went through enter_from_user_mode() >> which reactivates RCU > > I have to double-check... The NO_HZ_FULL case transitioning to/from > userspace is entirely non-preemptible, correct? (After rcu_user_enter() > and before rcu_user_exit(), respectively.) Yes. It runs with interrupts disabled down to the actual return (sysret, iret). Thanks, tglx