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Thu, 14 Oct 2021 16:43:42 -0700 (PDT) Received: from t490s ([209.132.188.80]) by smtp.gmail.com with ESMTPSA id lp9sm3827955pjb.35.2021.10.14.16.43.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 14 Oct 2021 16:43:41 -0700 (PDT) Date: Fri, 15 Oct 2021 07:43:37 +0800 From: Peter Xu To: Lin Ma Subject: Re: [PATCH 0/3] Postcopy migration: Add userfaultfd- user-mode-only capability Message-ID: References: <20211014091551.15201-1-lma@suse.com> MIME-Version: 1.0 In-Reply-To: <20211014091551.15201-1-lma@suse.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=peterx@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Received-SPF: pass client-ip=170.10.133.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.049, 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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-devel@nongnu.org, dgilbert@redhat.com, quintela@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 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, -- Peter Xu