linux-kernel - Re: [PATCH 0/1] uio_pci_generic: extensions to allow access for non-privileged processes

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: <201004011218.28002.pugs@lyon-about.com>
Date:	Thu, 1 Apr 2010 12:18:27 -0700
From:	Tom Lyon <pugs@...n-about.com>
To:	Joerg Roedel <joro@...tes.org>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/1] uio_pci_generic: extensions to allow access for non-privileged processes

On Thursday 01 April 2010 09:07:47 am Joerg Roedel wrote:
> On Thu, Apr 01, 2010 at 08:40:34AM -0700, Tom Lyon wrote:
> > On Thursday 01 April 2010 05:52:18 am Joerg Roedel wrote:
> > > > The point of this patch is to beef up the uio_pci_generic driver so
> > > > that a non-privileged user process can run a user level driver for
> > > > most PCIe devices. This can only be safe if there is an IOMMU in the
> > > > system with per-device domains.  Privileged users (CAP_SYS_RAWIO) are
> > > > allowed if there is no IOMMU.
> > >
> > > If you rely on an IOMMU you can use the IOMMU-API instead of the
> > > DMA-API for dma mappings. This change makes this driver suitable for
> > > KVM use too. If the interface is designed clever enough we can even use
> > > it for IOMMU emulation for pass-through devices.
> >
> > The use with privileged processes and no IOMMUs is still quite useful, so
> > I'd rather stick with the DMA interface.
>
> For the KVM use-case we need to be able to specify the io virtual
> address for a given process virtual address. This is not possible with
> the dma-api interface. So if we want to have uio-dma without an hardware
> iommu we need two distinct interfaces for userspace to cover all
> use-cases. I don't think its worth it to have two interfaces.
>
> 	Joerg

I started to add that capability but then realized that the IOMMU API also 
doesn't allow it. The map function allows a range of physically contiguous 
pages, not virtual.

My preferred approach would be to add a DMA_ATTR that would request allocation 
of DMA at a specific device/iommu address.
--
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/