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=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 BF4E3C2BB1D for ; Mon, 6 Apr 2020 20:25:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9F92D206B8 for ; Mon, 6 Apr 2020 20:25:13 +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="ysD9wHAa" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726331AbgDFUZN (ORCPT ); Mon, 6 Apr 2020 16:25:13 -0400 Received: from merlin.infradead.org ([205.233.59.134]:38608 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725957AbgDFUZM (ORCPT ); Mon, 6 Apr 2020 16:25:12 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.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; bh=xuOwKkylxNWAK5JsGTSzYpMwNioJNBL3cpLgcRJMmIk=; b=ysD9wHAaYXhY4cbstXONp2HSoW ZSVzDAAVy+rmG0HeJt4CI83tugugTQjr1ZpvMkO5a0H9iRDmQCB0tBMppX3vn+xkSA+f9r5y/4D+N XI/qoOaVGp0oAcDWow6rzk2Sv/6zuEdVdRg/OWiDaPzvKYMiJfazQjJ8y3wjDp//Pv0PvZPZ8GQWc 4Kc//4QWnNUWrPTzzWJeLwf4Q4WWX6YKApc+oN83tSFVBvdUFGTCgBXFRax1iIqMlPrkn7EprdP0r 5eDF59CRjuRtlq37yzNCNOJHYmVq0HOIgBLwIBhb0SYvsLUP/JlGaI/kMLJ2qtgoBapjoiDOOxWp9 vr0XqWKw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jLYIu-0006Z3-Ut; Mon, 06 Apr 2020 20:25:09 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id 5F1C6983962; Mon, 6 Apr 2020 22:25:05 +0200 (CEST) Date: Mon, 6 Apr 2020 22:25:05 +0200 From: Peter Zijlstra To: Vivek Goyal Cc: Thomas Gleixner , Andy Lutomirski , Paolo Bonzini , LKML , X86 ML , kvm list , stable Subject: Re: [PATCH v2] x86/kvm: Disable KVM_ASYNC_PF_SEND_ALWAYS Message-ID: <20200406202505.GO2452@worktop.programming.kicks-ass.net> References: <87a74s9ehb.fsf@nanos.tec.linutronix.de> <87wo7v8g4j.fsf@nanos.tec.linutronix.de> <877dzu8178.fsf@nanos.tec.linutronix.de> <37440ade-1657-648b-bf72-2b8ca4ac21ce@redhat.com> <871rq199oz.fsf@nanos.tec.linutronix.de> <87d09l73ip.fsf@nanos.tec.linutronix.de> <20200309202215.GM12561@hirez.programming.kicks-ass.net> <20200406190951.GA19259@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200406190951.GA19259@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Mon, Apr 06, 2020 at 03:09:51PM -0400, Vivek Goyal wrote: > On Mon, Mar 09, 2020 at 09:22:15PM +0100, Peter Zijlstra wrote: > > On Mon, Mar 09, 2020 at 08:05:18PM +0100, Thomas Gleixner wrote: > > > Andy Lutomirski writes: > > > > > > I'm okay with the save/restore dance, I guess. It's just yet more > > > > entry crud to deal with architecture nastiness, except that this > > > > nastiness is 100% software and isn't Intel/AMD's fault. > > > > > > And we can do it in C and don't have to fiddle with it in the ASM > > > maze. > > > > Right; I'd still love to kill KVM_ASYNC_PF_SEND_ALWAYS though, even if > > we do the save/restore in do_nmi(). That is some wild brain melt. Also, > > AFAIK none of the distros are actually shipping a PREEMPT=y kernel > > anyway, so killing it shouldn't matter much. > > It will be nice if we can retain KVM_ASYNC_PF_SEND_ALWAYS. I have another > use case outside CONFIG_PREEMPT. > > I am trying to extend async pf interface to also report page fault errors > to the guest. Then please start over and design a sane ParaVirt Fault interface. The current one is utter crap.