From: "Michael S. Tsirkin" <mst@redhat.com>
To: Paul Brook <paul@codesourcery.com>
Cc: amit.shah@redhat.com, quintela@redhat.com, qemu-devel@nongnu.org,
kraxel@redhat.com
Subject: Re: [Qemu-devel] Re: [PATCHv2 09/12] vhost: vhost net support
Date: Sun, 28 Feb 2010 17:37:50 +0200 [thread overview]
Message-ID: <20100228153749.GD28921@redhat.com> (raw)
In-Reply-To: <201002281523.06717.paul@codesourcery.com>
On Sun, Feb 28, 2010 at 03:23:06PM +0000, Paul Brook wrote:
> > So guest can cause vhost to write to a wrong place in RAM, but it can
> > just pass a wrong address directly.
>
> That's not the point. Obviously any DMA capable device can be used to
> compromise a system. However if a device writes to address B after being told
> to write to address A, then you have a completely broken system.
Yes, but I do not see how this can happen with vhost backed to virtio.
> > As long as vhost does not access a
> > non-RAM address, we are definitely fine.
>
> Why does it matter what it's changed to? The virtio DMA addresses guest
> physical addresses. If guest physical address mappings change then the virtio
> device must respect those changes. The extreme case is a system with an IOMMU
> (not currently implemented in QEMU). In that case it's likely that physical-
> RAM mappings will change frequently.
>
> Paul
Yes, but this is already supported. The one thing that my patches assume
does not change while device is active, is physical to qemu virtual
mapping for virtio ring.
Since virtio device is allowed to access the ring at any time,
such changes would only legal when device is not active IMO,
and my code translates physical to virtual when device is
made active.
So I do not see a bug.
--
MST
next prev parent reply other threads:[~2010-02-28 15:41 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-02-25 18:27 [Qemu-devel] [PATCHv2 00/12] vhost-net: upstream integration Michael S. Tsirkin
2010-02-25 18:27 ` [Qemu-devel] [PATCHv2 05/12] virtio: add APIs for queue fields Michael S. Tsirkin
2010-02-25 18:49 ` Blue Swirl
2010-02-26 14:53 ` Michael S. Tsirkin
2010-02-25 19:25 ` [Qemu-devel] " Anthony Liguori
2010-02-26 8:46 ` Gleb Natapov
2010-02-25 18:28 ` [Qemu-devel] [PATCHv2 09/12] vhost: vhost net support Michael S. Tsirkin
2010-02-25 19:04 ` [Qemu-devel] " Juan Quintela
2010-02-26 14:32 ` Michael S. Tsirkin
2010-02-26 14:38 ` Anthony Liguori
2010-02-26 14:54 ` Michael S. Tsirkin
2010-02-25 19:44 ` Anthony Liguori
2010-02-26 14:49 ` Michael S. Tsirkin
2010-02-26 15:18 ` Anthony Liguori
2010-02-27 19:38 ` Michael S. Tsirkin
2010-02-28 1:59 ` Paul Brook
2010-02-28 10:15 ` Michael S. Tsirkin
2010-02-28 12:45 ` Paul Brook
2010-02-28 14:44 ` Michael S. Tsirkin
2010-02-28 15:23 ` Paul Brook
2010-02-28 15:37 ` Michael S. Tsirkin [this message]
2010-02-28 16:02 ` Anthony Liguori
2010-02-25 18:28 ` [Qemu-devel] [PATCHv2 02/12] kvm: add API to set ioeventfd Michael S. Tsirkin
2010-02-25 19:19 ` [Qemu-devel] " Anthony Liguori
2010-03-02 17:41 ` Michael S. Tsirkin
2010-02-25 18:28 ` [Qemu-devel] [PATCHv2 04/12] virtio: add notifier support Michael S. Tsirkin
2010-02-25 18:28 ` [Qemu-devel] [PATCHv2 01/12] tap: add interface to get device fd Michael S. Tsirkin
2010-02-25 18:28 ` [Qemu-devel] [PATCHv2 07/12] virtio: move typedef to qemu-common Michael S. Tsirkin
2010-02-25 18:28 ` [Qemu-devel] [PATCHv2 10/12] tap: add vhost/vhostfd options Michael S. Tsirkin
2010-02-25 19:47 ` [Qemu-devel] " Anthony Liguori
2010-02-26 14:51 ` Michael S. Tsirkin
2010-02-26 15:23 ` Anthony Liguori
2010-02-27 19:44 ` Michael S. Tsirkin
2010-02-28 16:08 ` Anthony Liguori
2010-02-28 17:19 ` Michael S. Tsirkin
2010-02-28 20:57 ` Anthony Liguori
2010-02-28 21:01 ` Michael S. Tsirkin
2010-02-28 22:38 ` Anthony Liguori
2010-02-28 22:39 ` Paul Brook
2010-03-01 19:27 ` Michael S. Tsirkin
2010-03-01 21:54 ` Anthony Liguori
2010-03-02 9:57 ` Michael S. Tsirkin
2010-03-02 14:07 ` Anthony Liguori
2010-03-02 14:33 ` Paul Brook
2010-03-02 14:39 ` Anthony Liguori
2010-03-02 14:55 ` Paul Brook
2010-03-02 15:33 ` Anthony Liguori
2010-03-02 15:53 ` Paul Brook
2010-03-02 15:56 ` Michael S. Tsirkin
2010-03-02 16:12 ` Anthony Liguori
2010-03-02 16:21 ` Marcelo Tosatti
2010-03-02 16:12 ` Marcelo Tosatti
2010-03-02 16:56 ` Anthony Liguori
2010-03-02 17:00 ` Michael S. Tsirkin
2010-03-02 18:00 ` Marcelo Tosatti
2010-03-02 18:13 ` Anthony Liguori
2010-03-02 22:41 ` Paul Brook
2010-03-03 14:15 ` Anthony Liguori
2010-03-03 14:43 ` Paul Brook
2010-03-03 16:24 ` Marcelo Tosatti
2010-02-25 18:28 ` [Qemu-devel] [PATCHv2 11/12] tap: add API to retrieve vhost net header Michael S. Tsirkin
2010-02-25 18:28 ` [Qemu-devel] [PATCHv2 06/12] virtio: add set_status callback Michael S. Tsirkin
2010-02-25 18:28 ` [Qemu-devel] [PATCHv2 08/12] virtio-pci: fill in notifier support Michael S. Tsirkin
2010-02-25 19:30 ` [Qemu-devel] " Anthony Liguori
2010-02-28 20:02 ` Michael S. Tsirkin
2010-02-25 18:28 ` [Qemu-devel] [PATCHv2 03/12] notifier: event notifier implementation Michael S. Tsirkin
2010-02-25 19:22 ` [Qemu-devel] " Anthony Liguori
2010-02-28 19:59 ` Michael S. Tsirkin
2010-02-25 18:28 ` [Qemu-devel] [PATCHv2 12/12] virtio-net: vhost net support Michael S. Tsirkin
2010-02-25 19:49 ` [Qemu-devel] Re: [PATCHv2 00/12] vhost-net: upstream integration Anthony Liguori
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