Message-ID: <1371441361.21896.152.camel@pasglop>
Subject: Re: [PATCH 3/4] KVM: PPC: Add support for IOMMU in-kernel handling
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: Alexey Kardashevskiy <aik@ozlabs.ru>, linuxppc-dev@lists.ozlabs.org,
        David Gibson <david@gibson.dropbear.id.au>,
        Alexander Graf <agraf@suse.de>, Paul Mackerras <paulus@samba.org>,
        kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        kvm-ppc@vger.kernel.org
Date: Mon, 17 Jun 2013 13:56:01 +1000
In-Reply-To: <1371438800.22681.38.camel@ul30vt.home>
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On Sun, 2013-06-16 at 21:13 -0600, Alex Williamson wrote:

> IOMMU groups themselves don't provide security, they're accessed by
> interfaces like VFIO, which provide the security.  Given a brief look, I
> agree, this looks like a possible backdoor.  The typical VFIO way to
> handle this would be to pass a VFIO file descriptor here to prove that
> the process has access to the IOMMU group.  This is how /dev/vfio/vfio
> gains the ability to setup an IOMMU domain an do mappings with the
> SET_CONTAINER ioctl using a group fd.  Thanks,

How do you envision that in the kernel ? IE. I'm in KVM code, gets that
vfio fd, what do I do with it ?

Basically, KVM needs to know that the user is allowed to use that iommu
group. I don't think we want KVM however to call into VFIO directly
right ?

Cheers,
Ben.


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