linux-kernel - Re: [PATCH v3 0/3] virtio DMA API core stuff

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20151120094616-mutt-send-email-mst@redhat.com>
Date:	Fri, 20 Nov 2015 09:47:25 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Sebastian Ott <sebott@...ux.vnet.ibm.com>,
	linux-s390 <linux-s390@...r.kernel.org>,
	Cornelia Huck <cornelia.huck@...ibm.com>,
	Joerg Roedel <jroedel@...e.de>,
	Linux Virtualization <virtualization@...ts.linux-foundation.org>,
	Christoph Hellwig <hch@....de>,
	David Woodhouse <dwmw2@...radead.org>,
	KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH v3 0/3] virtio DMA API core stuff

On Fri, Nov 20, 2015 at 08:56:46AM +0200, Michael S. Tsirkin wrote:
> On Thu, Nov 19, 2015 at 01:59:05PM -0800, Andy Lutomirski wrote:
> > On Nov 19, 2015 5:45 AM, "Michael S. Tsirkin" <mst@...hat.com> wrote:
> > >
> > > On Tue, Oct 27, 2015 at 11:38:57PM -0700, Andy Lutomirski wrote:
> > > > This switches virtio to use the DMA API unconditionally.  I'm sure
> > > > it breaks things, but it seems to work on x86 using virtio-pci, with
> > > > and without Xen, and using both the modern 1.0 variant and the
> > > > legacy variant.
> > >
> > > So thinking hard about it, I don't see any real drawbacks to making this
> > > conditional on a new feature bit, that Xen can then set..
> > 
> > Can you elaborate?  If I run QEMU, hosting Xen, hosting Linux, and the
> > virtio device is provided by QEMU, then how does Xen set the bit?
> 
> You would run QEMU with the appropriate flag. E.g.
> -global virtio-pci,use_platform_dma=on

Or Xen code within QEMU can tweak this global internally
so users don't need to care.

> > Similarly, how would Xen set the bit for a real physical device?
> > 
> > 
> > --Andy
> 
> There's no need to set bits for physical devices I think: from security
> point of view, using them from a VM isn't very different from using them
> from host.
> 
> 
> 
> -- 
> MST
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/