From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43885) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fxTxH-0002Kg-0l for qemu-devel@nongnu.org; Wed, 05 Sep 2018 05:18:32 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fxTxC-00007w-NW for qemu-devel@nongnu.org; Wed, 05 Sep 2018 05:18:30 -0400 Received: from mail-ve1eur01on0123.outbound.protection.outlook.com ([104.47.1.123]:29152 helo=EUR01-VE1-obe.outbound.protection.outlook.com) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fxTxB-0008Bi-Vp for qemu-devel@nongnu.org; Wed, 05 Sep 2018 05:18:26 -0400 References: <20180718154200.26777-1-dplotnikov@virtuozzo.com> <20180720092717.GB16910@xz-mi> <4c3e07f4-ba82-9b88-6d32-4407b10a9926@virtuozzo.com> <20180905033255.GA16809@xz-x1> From: Denis Plotnikov Message-ID: Date: Wed, 5 Sep 2018 12:18:09 +0300 MIME-Version: 1.0 In-Reply-To: <20180905033255.GA16809@xz-x1> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v1 00/17] Background snapshots List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Xu Cc: dgilbert@redhat.com, quintela@redhat.com, pbonzini@redhat.com, qemu-devel@nongnu.org Hi Peter, Thanks for the reply. Ok, I understand about tcg. So my only option is to wait for userfaultfd-wp. Do you know if anyone is currently working on this? And if so, then is there any estimations when the userfaultfd is ready? Denis On 05.09.2018 06:32, Peter Xu wrote: > 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, > -- Best, Denis