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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9F3BEC433EF for ; Fri, 15 Oct 2021 05:39:39 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 1D5E560F21 for ; Fri, 15 Oct 2021 05:39:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 1D5E560F21 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=suse.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:36520 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mbFwQ-0005jx-55 for qemu-devel@archiver.kernel.org; Fri, 15 Oct 2021 01:39:38 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:49824) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mbFv2-00051b-LG for qemu-devel@nongnu.org; Fri, 15 Oct 2021 01:38:12 -0400 Received: from smtp-out1.suse.de ([195.135.220.28]:53776) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1mbFv0-0007gb-3P for qemu-devel@nongnu.org; Fri, 15 Oct 2021 01:38:12 -0400 Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id D2D9721969; Fri, 15 Oct 2021 05:38:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1634276286; h=from:from:reply-to: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=On2XPk4f/qSBpclEHuEOCSgzh1aS796y+eR37yE5W08=; b=xXjWz2xoCNC0nJl8h13sKE0iwgjxtoqDZ5/nTnvnGqcf97+Xs6s6qG94+RdDcJMD86vAtw Cue4IusdC2FAV977jTKehDnQERrZVOqmMeR0BFpcS1615Jgpo95nrv3IInfp323jEkN4BT DZCp2aHdPa1+1KxreuNXFnxGCe2azng= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1634276286; h=from:from:reply-to: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=On2XPk4f/qSBpclEHuEOCSgzh1aS796y+eR37yE5W08=; b=bYPMRT6HoOZEk8LG0PtnoVwyJmBP76p2N8aru05zVpkwvq50hPhFGe+p+k0zqutKbFd6WP 5ER1fM7oJEmqvFDA== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id C895413481; Fri, 15 Oct 2021 05:38:06 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 5X63ML4TaWHIQAAAMHmgww (envelope-from ); Fri, 15 Oct 2021 05:38:06 +0000 MIME-Version: 1.0 Date: Fri, 15 Oct 2021 13:38:06 +0800 From: lma To: Peter Xu Subject: Re: [PATCH 0/3] Postcopy migration: Add userfaultfd- user-mode-only capability In-Reply-To: References: <20211014091551.15201-1-lma@suse.com> User-Agent: Roundcube Webmail Message-ID: <7c0161fab24b06fa249061780a7f30d4@suse.de> X-Sender: lma@suse.de Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=195.135.220.28; envelope-from=lma@suse.de; helo=smtp-out1.suse.de X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, 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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: quintela@redhat.com, qemu-devel@nongnu.org, lma@suse.de, dgilbert@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 在 2021-10-15 07:43，Peter Xu 写道： > On Thu, Oct 14, 2021 at 05:15:48PM +0800, Lin Ma wrote: >> Since kernel v5.11, Unprivileged user (without SYS_CAP_PTRACE >> capability) >> must pass UFFD_USER_MODE_ONLY to userfaultd in case >> unprivileged_userfaultfd >> sysctl knob is 0. >> Please refer to https://lwn.net/Articles/819834/ and the kernel >> commits: >> 37cd0575 userfaultfd: add UFFD_USER_MODE_ONLY >> d0d4730a userfaultfd: add user-mode only option to >> unprivileged_userfaultfd sysctl knob >> >> This patch set adds a migration capability to pass UFFD_USER_MODE_ONLY >> for postcopy migration. > > Then it's at least no KVM, no vhost, am I right? Could I ask is there > a real > user behind this? Thanks, Well, The "user-mode-only" has nothing to do with qemu's user-mode emulation. The unprivileged_userfaultfd sysctl knob controls whether unprivileged users can use the userfaultfd system calls. set it to 1 to allow unprivileged users to use the userfaultfd system calls. set it to 0 to restrict userfaultfd to only privileged users (with SYS_CAP_PTRACE capability). If host's unprivileged_userfaultfd sysctl knob is 0(The default value of this knob is changed to 0 since host kernel v5.11): Qemu must pass the UFFD_USER_MODE_ONLY flag when creating userfaultfd object for postcopy migration in case qemu runs as unprivileged user. Before host kernel v5.11, If host's unprivileged_userfaultfd sysctl knob is 0, Then postcopy migration is not allowed in case qemu runs as unprivileged user. Thanks, Lin