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=-3.8 required=3.0 tests=BAYES_00, 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 08C93C433B4 for ; Wed, 12 May 2021 08:37:45 +0000 (UTC) Received: from smtp4.osuosl.org (smtp4.osuosl.org [140.211.166.137]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 4F6CC610F8 for ; Wed, 12 May 2021 08:37:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4F6CC610F8 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=8bytes.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=virtualization-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id D6C7D404B4; Wed, 12 May 2021 08:37:43 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp4.osuosl.org ([127.0.0.1]) by localhost (smtp4.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id JVhnKryWCMkm; Wed, 12 May 2021 08:37:42 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by smtp4.osuosl.org (Postfix) with ESMTP id 36E8740467; Wed, 12 May 2021 08:37:42 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id EB599C000E; Wed, 12 May 2021 08:37:41 +0000 (UTC) Received: from smtp2.osuosl.org (smtp2.osuosl.org [IPv6:2605:bc80:3010::133]) by lists.linuxfoundation.org (Postfix) with ESMTP id 1D5CCC0001 for ; Wed, 12 May 2021 08:37:41 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp2.osuosl.org (Postfix) with ESMTP id F3518402D4 for ; Wed, 12 May 2021 08:37:40 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp2.osuosl.org ([127.0.0.1]) by localhost (smtp2.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Ov1jWMHoPSQw for ; Wed, 12 May 2021 08:37:40 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.8.0 Received: from theia.8bytes.org (8bytes.org [IPv6:2a01:238:4383:600:38bc:a715:4b6d:a889]) by smtp2.osuosl.org (Postfix) with ESMTPS id 4BB9140015 for ; Wed, 12 May 2021 08:37:40 +0000 (UTC) Received: by theia.8bytes.org (Postfix, from userid 1000) id E8C872A5; Wed, 12 May 2021 10:37:37 +0200 (CEST) Date: Wed, 12 May 2021 10:37:34 +0200 From: 'Joerg Roedel' To: David Laight Subject: Re: [PATCH 3/6] x86/sev-es: Use __put_user()/__get_user Message-ID: References: <20210512075445.18935-1-joro@8bytes.org> <20210512075445.18935-4-joro@8bytes.org> <0496626f018d4d27a8034a4822170222@AcuMS.aculab.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <0496626f018d4d27a8034a4822170222@AcuMS.aculab.com> Cc: "kvm@vger.kernel.org" , Peter Zijlstra , Dave Hansen , "virtualization@lists.linux-foundation.org" , Arvind Sankar , "hpa@zytor.com" , Jiri Slaby , "x86@kernel.org" , David Rientjes , Martin Radev , Tom Lendacky , Joerg Roedel , Kees Cook , Cfir Cohen , Hyunwook Baek , "linux-coco@lists.linux.dev" , Andy Lutomirski , Dan Williams , Juergen Gross , Mike Stunes , Sean Christopherson , "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" , Masami Hiramatsu , Erdem Aktas X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" On Wed, May 12, 2021 at 08:04:33AM +0000, David Laight wrote: > That can't be right at all. > __put/get_user() are only valid on user addresses and will try to > fault in a missing page - so can sleep. Yes, in general these functions can sleep, but not in this context. They are called in atomic context and the page-fault handler will notice that and goes down the __bad_area_nosemaphore() path and only do the fixup. I also thought about adding page_fault_disable()/page_fault_enable() calls, but being in atomic context is enough according to the faulthandler_disabled() implementation. This is exactly what is needed here. All I want to know is whether a fault happened or not, the page-fault handler must not try to fix the fault in any way. If a fault happens it is later fixed up in vc_forward_exception(). > At best this is abused the calls. Yes, but that is only due to the naming of these functions. In this case they do exactly what is needed. Regards, Joerg _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization