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=DKIMWL_WL_HIGH,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 84AABC3F2D2 for ; Mon, 2 Mar 2020 10:41:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4B7092187F for ; Mon, 2 Mar 2020 10:41:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Jb59s3/M" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727452AbgCBKl1 (ORCPT ); Mon, 2 Mar 2020 05:41:27 -0500 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:52961 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726874AbgCBKl0 (ORCPT ); Mon, 2 Mar 2020 05:41:26 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1583145685; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=W/No+zSqneGbjc27RGNY0R0gIKfmegvgk6I94PCXiQI=; b=Jb59s3/MuVttVOpl+gBeLwdTafjUpK8T1oMgbKeQRp6GJmoJ8Vyh5Su98GextM3cG2Xv9d aBPAp8TRVRDETYGMvN7If9YSRvM51yLoU5whVNGOtkY+8zWcLP1MsIiJlAXXOt/CrxVZeh AAQt2hksGGEEzuzDupGH/+pq888WnPc= Received: from mail-wr1-f69.google.com (mail-wr1-f69.google.com [209.85.221.69]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-287-41NwHy_-P8O0l55RBG6qtg-1; Mon, 02 Mar 2020 05:41:23 -0500 X-MC-Unique: 41NwHy_-P8O0l55RBG6qtg-1 Received: by mail-wr1-f69.google.com with SMTP id w6so5596294wrm.16 for ; Mon, 02 Mar 2020 02:41:23 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=W/No+zSqneGbjc27RGNY0R0gIKfmegvgk6I94PCXiQI=; b=oTKKY7MRSiGwSRgsvL3W7CslDtTcvz8AY/1dQG6J0MKAciEZf2OUg84ilvmmwj+Gcp 6rI8/CaihM8NZR+KQDxPWvADK52Y2mPHr1ablBghjgEOkQ+XLIXqnc8Ify6HrDqIxCOx 0WLB6qlNIR3zdj80SIGqkXtuX39N0+GRlOrUbnmrxOpXna409Kxe3PiUp94GKyBIgVVs 8AW7fdameDXwwJz0HZjeCfc+IJp4RPwh/eiZf7guA3erb5gzUwVsEetJGIrp6Fn2rT/r v4nPETZxylY7scw3CBEtHSPX3CxIyOXEoY9xcfcAUylxqrSGLrn5IXd2+rwEp9bJnLWW Ks+A== X-Gm-Message-State: APjAAAWvBW8H61WcUMY+ov4cYFB9vQVTjGJD5R5IQhTfN8qsLnIrZ4jv MwLYRqS9s/jKNpTgW5/THxWtt+zZD2QUZqBFIAK8BfcuG0i4/4bZc1HGL2+NB4Et2EM2qE6T8uo p5XlRthsLQrfndXFMJIaKKo2Z X-Received: by 2002:adf:ec0e:: with SMTP id x14mr20684969wrn.270.1583145682637; Mon, 02 Mar 2020 02:41:22 -0800 (PST) X-Google-Smtp-Source: APXvYqxr5BG762XJibpFKMG4qKy++MMibwFPZUGzvUBIxE+6bF6Hv9ol6loBGjhblNJ67DPHLJxYFQ== X-Received: by 2002:adf:ec0e:: with SMTP id x14mr20684948wrn.270.1583145682375; Mon, 02 Mar 2020 02:41:22 -0800 (PST) Received: from [192.168.178.40] ([151.30.85.6]) by smtp.gmail.com with ESMTPSA id o18sm23121454wrv.60.2020.03.02.02.41.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 02 Mar 2020 02:41:21 -0800 (PST) Subject: Re: [PATCH v2] x86/kvm: Handle async page faults directly through do_page_fault() To: Nadav Amit , Andy Lutomirski Cc: LKML , x86 , kvm list References: <53626d08de5df34eacce80cb74f19a06fdc690c6.1582998497.git.luto@kernel.org> <34082A11-321D-4DF0-A076-7BBF332DCA66@gmail.com> From: Paolo Bonzini Message-ID: <328119b6-38a3-8b74-9e89-629977316ff4@redhat.com> Date: Mon, 2 Mar 2020 11:41:20 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <34082A11-321D-4DF0-A076-7BBF332DCA66@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/03/20 10:28, Nadav Amit wrote: > > Yet, this might be a slippery slope, making Linux optimized to run on KVM > (and maybe Xen). In other words, I wonder whether a similar change was > acceptable for a paravirtual feature that is only supported by a proprietary > hypervisor, such as Hyper-V or VMware. Your concern is understandable. I think in this case Andy's patch makes sense since there is a hooking mechanism that is used in exactly one case and there are no performance issues in removing it. In fact if more hypervisors implemented a #PF extension I would keep the static branch, but use it to choose between a pvop and the default case; this would be a much more localized change, so arguably better than trap_init. Paolo