From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:51241) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ghXPY-0005uU-CE for qemu-devel@nongnu.org; Thu, 10 Jan 2019 05:18:10 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ghXPX-0005hI-3N for qemu-devel@nongnu.org; Thu, 10 Jan 2019 05:18:04 -0500 Received: from mx2.suse.de ([195.135.220.15]:33736 helo=mx1.suse.de) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ghXPV-0005ga-O0 for qemu-devel@nongnu.org; Thu, 10 Jan 2019 05:18:03 -0500 Date: Thu, 10 Jan 2019 11:17:57 +0100 From: Jan Kara Message-ID: <20190110101757.GC15790@quack2.suse.cz> References: <20190109144736.17452-1-pagupta@redhat.com> <20190110012617.GA4205@dastard> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190110012617.GA4205@dastard> Subject: Re: [Qemu-devel] [PATCH v3 0/5] kvm "virtio pmem" device List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Dave Chinner Cc: Pankaj Gupta , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, qemu-devel@nongnu.org, linux-nvdimm@ml01.01.org, linux-fsdevel@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-acpi@vger.kernel.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, jack@suse.cz, stefanha@redhat.com, dan.j.williams@intel.com, riel@surriel.com, nilal@redhat.com, kwolf@redhat.com, pbonzini@redhat.com, zwisler@kernel.org, vishal.l.verma@intel.com, dave.jiang@intel.com, david@redhat.com, jmoyer@redhat.com, xiaoguangrong.eric@gmail.com, hch@infradead.org, mst@redhat.com, jasowang@redhat.com, lcapitulino@redhat.com, imammedo@redhat.com, eblake@redhat.com, willy@infradead.org, tytso@mit.edu, adilger.kernel@dilger.ca, darrick.wong@oracle.com, rjw@rjwysocki.net On Thu 10-01-19 12:26:17, Dave Chinner wrote: > On Wed, Jan 09, 2019 at 08:17:31PM +0530, Pankaj Gupta wrote: > > This patch series has implementation for "virtio pmem". > > "virtio pmem" is fake persistent memory(nvdimm) in guest > > which allows to bypass the guest page cache. This also > > implements a VIRTIO based asynchronous flush mechanism. > > Hmmmm. Sharing the host page cache direct into the guest VM. Sounds > like a good idea, but..... > > This means the guest VM can now run timing attacks to observe host > side page cache residency, and depending on the implementation I'm > guessing that the guest will be able to control host side page > cache eviction, too (e.g. via discard or hole punch operations). > > Which means this functionality looks to me like a new vector for > information leakage into and out of the guest VM via guest > controlled host page cache manipulation. > > https://arxiv.org/pdf/1901.01161 > > I might be wrong, but if I'm not we're going to have to be very > careful about how guest VMs can access and manipulate host side > resources like the page cache..... Right. Thinking about this I would be more concerned about the fact that guest can effectively pin amount of host's page cache upto size of the device/file passed to guest as PMEM, can't it Pankaj? Or is there some QEMU magic that avoids this? Honza -- Jan Kara SUSE Labs, CR