From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f200.google.com (mail-qt0-f200.google.com [209.85.216.200]) by kanga.kvack.org (Postfix) with ESMTP id 82A6B2806CB for ; Thu, 13 Apr 2017 21:50:56 -0400 (EDT) Received: by mail-qt0-f200.google.com with SMTP id r49so19612803qta.22 for ; Thu, 13 Apr 2017 18:50:56 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id i17si469478qkh.295.2017.04.13.18.50.55 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 13 Apr 2017 18:50:55 -0700 (PDT) Date: Fri, 14 Apr 2017 04:50:48 +0300 From: "Michael S. Tsirkin" Subject: Re: [PATCH v9 0/5] Extend virtio-balloon for fast (de)inflating & fast live migration Message-ID: <20170414044515-mutt-send-email-mst@kernel.org> References: <1492076108-117229-1-git-send-email-wei.w.wang@intel.com> <20170413204411.GJ784@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170413204411.GJ784@bombadil.infradead.org> Sender: owner-linux-mm@kvack.org List-ID: To: Matthew Wilcox Cc: Wei Wang , virtio-dev@lists.oasis-open.org, linux-kernel@vger.kernel.org, qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, linux-mm@kvack.org, david@redhat.com, dave.hansen@intel.com, cornelia.huck@de.ibm.com, akpm@linux-foundation.org, mgorman@techsingularity.net, aarcange@redhat.com, amit.shah@redhat.com, pbonzini@redhat.com, liliang.opensource@gmail.com On Thu, Apr 13, 2017 at 01:44:11PM -0700, Matthew Wilcox wrote: > On Thu, Apr 13, 2017 at 05:35:03PM +0800, Wei Wang wrote: > > 2) transfer the guest unused pages to the host so that they > > can be skipped to migrate in live migration. > > I don't understand this second bit. You leave the pages on the free list, > and tell the host they're free. What's preventing somebody else from > allocating them and using them for something? Is the guest semi-frozen > at this point with just enough of it running to ask the balloon driver > to do things? There's missing documentation here. The way things actually work is host sends to guest a request for unused pages and then write-protects all memory. So guest isn't frozen but any changes will be detected by host. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org