From: Dan Williams <dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org> To: Pankaj Gupta <pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> Cc: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>, KVM list <kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, David Hildenbrand <david-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, linux-nvdimm <linux-nvdimm-y27Ovi1pjclAfugRpC6u6w@public.gmane.org>, Jason Wang <jasowang-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Dave Chinner <david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org>, Qemu Developers <qemu-devel-qX2TKyscuCcdnm+yROfE0A@public.gmane.org>, virtualization-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, adilger kernel <adilger.kernel-m1MBpc4rdrD3fQ9qLvQP4Q@public.gmane.org>, Ross Zwisler <zwisler-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Eric Blake <eblake-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, darrick wong <darrick.wong-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>, "Michael S. Tsirkin" <mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Matthew Wilcox <willy-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>, Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>, Linux ACPI <linux-acpi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, linux-ext4 <linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Rik van Riel <riel-ebMLmSuQjDVBDgjK7y7TUQ@public.gmane.org>, Stefan Hajnoczi <stefanha-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Igor Mammedov <imammedo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, lcapitulino-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, Kevin Wolf <kwolf-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Nitesh Narayan Lal <nilal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Theodore Ts'o <tytso-3s7WtUTddSA@public.gmane.org>, xiaoguangro Subject: Re: [PATCH v3 0/5] kvm "virtio pmem" device Date: Sat, 12 Jan 2019 17:43:26 -0800 [thread overview] Message-ID: <CAPcyv4hwcgTUpgNCefCGu4DvgkYBp5b=f+hJ+FC=s5APYKoycg@mail.gmail.com> (raw) In-Reply-To: <1354249849.63357171.1547343519970.JavaMail.zimbra-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> On Sat, Jan 12, 2019 at 5:38 PM Pankaj Gupta <pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote: > > > > > > > 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? > > Yes, guest will pin these host page cache pages using 'get_user_pages' by > elevating the page reference count. But these pages can be reclaimed by host > at any time when there is memory pressure. Wait, how can the guest pin the host pages? I would expect this to happen only when using vfio and device assignment. Otherwise, no the host can't reclaim a pinned page, that's the whole point of a pin to prevent the mm from reclaiming ownership. > KVM does not permanently pin pages. vfio does that but we are not using > it here. Right, so I'm confused by your pin assertion above.
WARNING: multiple messages have this Message-ID (diff)
From: Dan Williams <dan.j.williams@intel.com> To: Pankaj Gupta <pagupta@redhat.com> Cc: Jan Kara <jack@suse.cz>, Dave Chinner <david@fromorbit.com>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, KVM list <kvm@vger.kernel.org>, Qemu Developers <qemu-devel@nongnu.org>, linux-nvdimm <linux-nvdimm@ml01.01.org>, linux-fsdevel <linux-fsdevel@vger.kernel.org>, virtualization@lists.linux-foundation.org, Linux ACPI <linux-acpi@vger.kernel.org>, linux-ext4 <linux-ext4@vger.kernel.org>, linux-xfs <linux-xfs@vger.kernel.org>, Stefan Hajnoczi <stefanha@redhat.com>, Rik van Riel <riel@surriel.com>, Nitesh Narayan Lal <nilal@redhat.com>, Kevin Wolf <kwolf@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, Ross Zwisler <zwisler@kernel.org>, vishal l verma <vishal.l.verma@intel.com>, dave jiang <dave.jiang@intel.com>, David Hildenbrand <david@redhat.com>, jmoyer <jmoyer@redhat.com>, xiaoguangrong eric <xiaoguangrong.eric@gmail.com>, Christoph Hellwig <hch@infradead.org>, "Michael S. Tsirkin" <mst@redhat.com>, Jason Wang <jasowang@redhat.com>, lcapitulino@redhat.com, Igor Mammedov <imammedo@redhat.com>, Eric Blake <eblake@redhat.com>, Matthew Wilcox <willy@infradead.org>, "Theodore Ts'o" <tytso@mit.edu>, adilger kernel <adilger.kernel@dilger.ca>, darrick wong <darrick.wong@oracle.com>, "Rafael J. Wysocki" <rjw@rjwysocki.net> Subject: Re: [PATCH v3 0/5] kvm "virtio pmem" device Date: Sat, 12 Jan 2019 17:43:26 -0800 [thread overview] Message-ID: <CAPcyv4hwcgTUpgNCefCGu4DvgkYBp5b=f+hJ+FC=s5APYKoycg@mail.gmail.com> (raw) Message-ID: <20190113014326.sKMLXBhz911O-HTZPgEQMM0W5CFokEhVvHrf5sTloW0@z> (raw) In-Reply-To: <1354249849.63357171.1547343519970.JavaMail.zimbra@redhat.com> On Sat, Jan 12, 2019 at 5:38 PM Pankaj Gupta <pagupta@redhat.com> wrote: > > > > > > > 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? > > Yes, guest will pin these host page cache pages using 'get_user_pages' by > elevating the page reference count. But these pages can be reclaimed by host > at any time when there is memory pressure. Wait, how can the guest pin the host pages? I would expect this to happen only when using vfio and device assignment. Otherwise, no the host can't reclaim a pinned page, that's the whole point of a pin to prevent the mm from reclaiming ownership. > KVM does not permanently pin pages. vfio does that but we are not using > it here. Right, so I'm confused by your pin assertion above.
next prev parent reply other threads:[~2019-01-13 1:43 UTC|newest] Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-01-09 14:47 [PATCH v3 0/5] kvm "virtio pmem" device Pankaj Gupta 2019-01-09 14:47 ` [PATCH v3 1/5] libnvdimm: nd_region flush callback support Pankaj Gupta 2019-01-09 14:47 ` [PATCH v3 2/5] virtio-pmem: Add virtio pmem driver Pankaj Gupta 2019-01-14 15:54 ` Michael S. Tsirkin 2019-01-14 15:54 ` Michael S. Tsirkin [not found] ` <20190114105314-mutt-send-email-mst-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> 2019-01-15 6:33 ` Pankaj Gupta 2019-01-15 6:33 ` Pankaj Gupta 2019-01-09 14:47 ` [PATCH v3 3/5] libnvdimm: add nd_region buffered dax_dev flag Pankaj Gupta 2019-01-09 14:47 ` [PATCH v3 4/5] ext4: disable map_sync for virtio pmem Pankaj Gupta 2019-01-09 14:47 ` [PATCH v3 5/5] xfs: " Pankaj Gupta 2019-01-09 14:47 ` Pankaj Gupta 2019-01-09 16:26 ` Darrick J. Wong 2019-01-09 18:08 ` Pankaj Gupta [not found] ` <20190109144736.17452-1-pagupta-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> 2019-01-10 1:26 ` [PATCH v3 0/5] kvm "virtio pmem" device Dave Chinner 2019-01-10 1:26 ` Dave Chinner 2019-01-10 2:40 ` Rik van Riel 2019-01-10 2:40 ` Rik van Riel 2019-01-10 10:17 ` Jan Kara 2019-01-10 10:17 ` Jan Kara [not found] ` <20190110101757.GC15790-4I4JzKEfoa/jFM9bn6wA6Q@public.gmane.org> 2019-01-13 1:38 ` Pankaj Gupta 2019-01-13 1:38 ` Pankaj Gupta [not found] ` <1354249849.63357171.1547343519970.JavaMail.zimbra-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> 2019-01-13 1:43 ` Dan Williams [this message] 2019-01-13 1:43 ` Dan Williams [not found] ` <CAPcyv4hwcgTUpgNCefCGu4DvgkYBp5b=f+hJ+FC=s5APYKoycg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2019-01-13 2:17 ` [Qemu-devel] " Pankaj Gupta 2019-01-13 2:17 ` Pankaj Gupta [not found] ` <540171952.63371441.1547345866585.JavaMail.zimbra-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> 2019-01-14 9:55 ` Jan Kara 2019-01-14 9:55 ` Jan Kara [not found] ` <20190114095520.GC13316-4I4JzKEfoa/jFM9bn6wA6Q@public.gmane.org> 2019-01-14 10:16 ` Pankaj Gupta 2019-01-14 10:16 ` Pankaj Gupta 2019-01-11 7:45 ` Pankaj Gupta 2019-01-11 7:45 ` Pankaj Gupta [not found] ` <1326478078.61913951.1547192704870.JavaMail.zimbra-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> 2019-01-13 23:29 ` Dave Chinner 2019-01-13 23:29 ` Dave Chinner 2019-01-13 23:38 ` Matthew Wilcox 2019-01-13 23:38 ` Matthew Wilcox [not found] ` <20190113233820.GX6310-PfSpb0PWhxZc2C7mugBRk2EX/6BAtgUQ@public.gmane.org> 2019-01-14 2:50 ` Dave Chinner 2019-01-14 2:50 ` Dave Chinner 2019-01-14 7:15 ` Pankaj Gupta 2019-01-14 7:15 ` Pankaj Gupta [not found] ` <942065073.64011540.1547450140670.JavaMail.zimbra-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> 2019-01-14 21:25 ` Dave Chinner 2019-01-14 21:25 ` Dave Chinner 2019-01-14 21:35 ` Dan Williams 2019-01-14 21:35 ` Dan Williams [not found] ` <CAPcyv4jtPcLV-s0sKNHwwk0ug7GLBV6699dpm1h3r2xSo879dg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org> 2019-01-14 22:21 ` Dave Chinner 2019-01-14 22:21 ` Dave Chinner 2019-01-15 2:19 ` Michael S. Tsirkin 2019-01-15 2:19 ` Michael S. Tsirkin [not found] ` <20190114205031-mutt-send-email-mst-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> 2019-01-15 5:37 ` [Qemu-devel] " Pankaj Gupta 2019-01-15 5:37 ` Pankaj Gupta 2019-01-15 5:35 ` Pankaj Gupta 2019-01-15 5:35 ` Pankaj Gupta [not found] ` <1684638419.64320214.1547530506805.JavaMail.zimbra-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> 2019-01-15 20:42 ` Dave Chinner 2019-01-15 20:42 ` Dave Chinner 2019-02-04 22:56 ` security implications of caching with virtio pmem (was Re: [PATCH v3 0/5] kvm "virtio pmem" device) Michael S. Tsirkin 2019-02-05 7:29 ` [Qemu-devel] " Pankaj Gupta 2019-02-06 14:00 ` David Hildenbrand 2019-02-06 18:01 ` Michael S. Tsirkin 2019-02-11 7:29 ` [Qemu-devel] " Pankaj Gupta 2019-02-11 22:29 ` Dave Chinner 2019-02-11 22:58 ` David Hildenbrand 2019-02-11 23:07 ` Michael S. Tsirkin -- strict thread matches above, loose matches on Subject: below -- 2019-01-09 13:50 [PATCH v3 0/5] kvm "virtio pmem" device Pankaj Gupta
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