From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kara Subject: Re: [PATCH v3 0/5] kvm "virtio pmem" device Date: Thu, 10 Jan 2019 11:17:57 +0100 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-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20190110012617.GA4205@dastard> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-nvdimm-bounces-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org Sender: "Linux-nvdimm" To: Dave Chinner Cc: jack-AlSwsSmVLrQ@public.gmane.org, kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, david-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, linux-nvdimm-y27Ovi1pjclAfugRpC6u6w@public.gmane.org, jasowang-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, qemu-devel-qX2TKyscuCcdnm+yROfE0A@public.gmane.org, virtualization-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, adilger.kernel-m1MBpc4rdrD3fQ9qLvQP4Q@public.gmane.org, zwisler-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, eblake-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, darrick.wong-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org, mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, willy-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, linux-acpi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, riel-ebMLmSuQjDVBDgjK7y7TUQ@public.gmane.org, stefanha-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, imammedo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, lcapitulino-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, kwolf-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, nilal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, tytso-3s7WtUTddSA@public.gmane.org, xiaoguangrong.eric-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, rjw-LthD3rsA81gm4RdzfppkhA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-xfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, pbonzini-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org List-Id: linux-nvdimm@lists.01.org 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