From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60903) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fxOZ3-0001Dz-Hy for qemu-devel@nongnu.org; Tue, 04 Sep 2018 23:33:10 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fxOZ0-0003Dj-4g for qemu-devel@nongnu.org; Tue, 04 Sep 2018 23:33:09 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:40016 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fxOYz-0003BY-Lt for qemu-devel@nongnu.org; Tue, 04 Sep 2018 23:33:05 -0400 Date: Wed, 5 Sep 2018 11:32:55 +0800 From: Peter Xu Message-ID: <20180905033255.GA16809@xz-x1> References: <20180718154200.26777-1-dplotnikov@virtuozzo.com> <20180720092717.GB16910@xz-mi> <4c3e07f4-ba82-9b88-6d32-4407b10a9926@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <4c3e07f4-ba82-9b88-6d32-4407b10a9926@virtuozzo.com> Subject: Re: [Qemu-devel] [PATCH v1 00/17] Background snapshots List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Denis Plotnikov Cc: dgilbert@redhat.com, quintela@redhat.com, pbonzini@redhat.com, qemu-devel@nongnu.org On Tue, Sep 04, 2018 at 04:00:31PM +0300, Denis Plotnikov wrote: > Hi Peter Hi, Denis, > > I moved the code to the repository > https://github.com/denis-plotnikov/qemu/tree/background-snapshot-kvm. > the current version includes fixes with respect to your comments for version > 1. > I moved KVM related patches to the end of the branch (formerly patch > series). > Since, the KVM patches and the other parts to modify (vhost an others) are > needless in favor of upcoming userfaltfd, > I would ask you to review the general framework which is able to work with > tcg. > > Thanks in advance! Thank you for pushing the tree. I might have made a mistake before that I thought this work is at least working for TCG, but I think I was wrong. The problem is (I'm trying to repeat Dave's question that you seems haven't yet answered): even for TCG there could be use cases where the process might access guest memory from the kernel space (e.g., vhost, or any system calls that with a guest memory buffer passed in). I'm afraid mprotect() and the whole signal-based mechanism cannot be able to address these page faults, then we'll encounter adhoc errors and we'll need to fix all these places up. Userfaultfd-wp should not have this problem. I think the general idea of the work is good, but I'm not sure whether we can merge the work if we don't settle these issues. Regards, -- Peter Xu