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 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id ACBA6C05027 for ; Thu, 26 Jan 2023 14:16:53 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pL33N-0006td-D5; Thu, 26 Jan 2023 09:16:37 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pL33L-0006tU-SN for qemu-devel@nongnu.org; Thu, 26 Jan 2023 09:16:35 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pL33K-0006ii-Hq for qemu-devel@nongnu.org; Thu, 26 Jan 2023 09:16:35 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1674742593; 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=Xp9QBeld717KsTDKw/ILMgnHH9pjDskMHfcGd8b49qU=; b=L9dyyFCWlRwvJ8nAhpIrGDtOl+mLRGKdU2UNKiKsy4+wU1DAYCpD1P/HSCMwBKcSLiVgH5 E90afXYW3KM14e22XgBG5IekSbK7Xro5YTK04YtlzUo2O+awfkexSXooK5yPcF5QSDtlOp 4nV20KHFKyEOM3IkU4B8fRXuNxrn3O0= Received: from mail-wr1-f71.google.com (mail-wr1-f71.google.com [209.85.221.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-561-CrZrZ8RQPwGZPxkwWbEyzQ-1; Thu, 26 Jan 2023 09:15:20 -0500 X-MC-Unique: CrZrZ8RQPwGZPxkwWbEyzQ-1 Received: by mail-wr1-f71.google.com with SMTP id v15-20020adfe4cf000000b002bf9413bc50so338675wrm.16 for ; Thu, 26 Jan 2023 06:15:15 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=user-agent:in-reply-to:content-transfer-encoding :content-disposition:mime-version:references:message-id:subject:cc :to:from:date:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=Xp9QBeld717KsTDKw/ILMgnHH9pjDskMHfcGd8b49qU=; b=c5CGFDMDCEOs4924IkliO4kqhd9bOP3dClEpUeFg+0J3o/QjexbGKcW/pR8Kn9fyId l9LdvpZAZtS1F0bfyVcTpGLg4uQ5zz7n6ArYBsUlmBN+22c7U4P5hCpTytsZBLhjGCKM HCnqNItBb8mrPX4/XbdrGZyjM5fp0Q2fW36oBV1PqgPkX5A+MvzjJE1FcGbYbZle5ArT gqCtj1uXBmBzM6OUH8TR9mXAGMp648n6/JGXGHmzph7RmWGQ3sbj2iGuZgPpqd/bfXe0 +++6WYWZOxFhRbXqc1ZXX6cRAgO7yc27EZxolS9WUDVd7HTnzHuT+4nkGRy2KPw/ENhm u5QA== X-Gm-Message-State: AFqh2kq6XWyejxGYGcTUEPZ2hKRr4keWzJTpHyATdze6U3JOvOsi2iss Sptl9O0DO/sItMdry8+Uq4MhUJFQ7xOmK8cEXImHWI7Pwsko8qkCRocnsZiV6CrqAcIdOVdgck6 5pZsJbkVlbnZQiEs= X-Received: by 2002:a05:600c:538e:b0:3da:516:19ed with SMTP id hg14-20020a05600c538e00b003da051619edmr35083484wmb.29.1674742514140; Thu, 26 Jan 2023 06:15:14 -0800 (PST) X-Google-Smtp-Source: AMrXdXtczbTSluIvvLd7Vi8lJ5n0len8h2tZzIm4TSLxykrLm+9lq4JX2oDLZEpRVUtWfTLjquBC4g== X-Received: by 2002:a05:600c:538e:b0:3da:516:19ed with SMTP id hg14-20020a05600c538e00b003da051619edmr35083470wmb.29.1674742513929; Thu, 26 Jan 2023 06:15:13 -0800 (PST) Received: from work-vm (ward-16-b2-v4wan-166627-cust863.vm18.cable.virginm.net. [81.97.203.96]) by smtp.gmail.com with ESMTPSA id u32-20020a05600c4d2000b003db0659c454sm1791717wmp.32.2023.01.26.06.15.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 26 Jan 2023 06:15:13 -0800 (PST) Date: Thu, 26 Jan 2023 14:15:11 +0000 From: "Dr. David Alan Gilbert" To: Michal =?iso-8859-1?B?UHLtdm96bu1r?= Cc: Peter Xu , qemu-devel@nongnu.org, Leonardo Bras Soares Passos , Juan Quintela Subject: Re: [PATCH 0/3] util/userfaultfd: Support /dev/userfaultfd Message-ID: References: <20230125224016.212529-1-peterx@redhat.com> <0f8ad497-202d-ae55-e468-77bb726a2699@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <0f8ad497-202d-ae55-e468-77bb726a2699@redhat.com> User-Agent: Mutt/2.2.9 (2022-11-12) Received-SPF: pass client-ip=170.10.129.124; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org * Michal Prívozník (mprivozn@redhat.com) wrote: > On 1/25/23 23:40, Peter Xu wrote: > > The new /dev/userfaultfd handle is superior to the system call with a > > better permission control and also works for a restricted seccomp > > environment. > > > > The new device was only introduced in v6.1 so we need a header update. > > > > Please have a look, thanks. > > I was wondering whether it would make sense/be possible for mgmt app > (libvirt) to pass FD for /dev/userfaultfd instead of QEMU opening it > itself. But looking into the code, libvirt would need to do that when > spawning QEMU because that's when QEMU itself initializes internal state > and queries userfaultfd caps. You also have to be careful about what the userfaultfd semantics are; I can't remember them - but if you open it in one process and pass it to another process, which processes address space are you trying to monitor? Dave > Michal > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK