From: Joerg Roedel <joro@8bytes.org>
To: Tom Lyon <pugs@lyon-about.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/1] uio_pci_generic: extensions to allow access for non-privileged processes
Date: Thu, 1 Apr 2010 22:09:10 +0200 [thread overview]
Message-ID: <20100401200910.GJ24846@8bytes.org> (raw)
In-Reply-To: <201004011218.28002.pugs@lyon-about.com>
On Thu, Apr 01, 2010 at 12:18:27PM -0700, Tom Lyon wrote:
> On Thursday 01 April 2010 09:07:47 am Joerg Roedel wrote:
> > 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.
>
> 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.
The IOMMU-API allows that. You have to convert the user-virtual
addresses into physical addresses first. The current KVM code
already does this and uses the IOMMU-API later. You can have a look at
the gfn_to_pfn() function for a way to implement this.
> My preferred approach would be to add a DMA_ATTR that would request
> allocation of DMA at a specific device/iommu address.
No, that would be feature duplication between both APIs. Not to mention
the implementation hell this additional dma-api feature would cause for
the iommu driver developers.
Joerg
next prev parent reply other threads:[~2010-04-01 20:09 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-01 0:08 [PATCH 0/1] uio_pci_generic: extensions to allow access for non-privileged processes Tom Lyon
2010-04-01 0:12 ` [PATCH 1/1] " Tom Lyon
2010-04-09 9:08 ` Joerg Roedel
2010-04-09 16:27 ` Tom Lyon
2010-04-01 9:09 ` [PATCH 0/1] " Avi Kivity
2010-04-01 15:39 ` Tom Lyon
2010-04-01 15:54 ` Avi Kivity
2010-04-01 16:06 ` Tom Lyon
2010-04-01 16:10 ` Avi Kivity
2010-04-01 19:24 ` Tom Lyon
2010-04-01 20:21 ` Joerg Roedel
2010-04-02 6:43 ` Avi Kivity
2010-04-02 17:05 ` Greg KH
2010-04-09 9:58 ` Avi Kivity
2010-04-09 16:34 ` Tom Lyon
2010-04-09 16:48 ` [PATCH 0/1] uio_pci_generic: extensions to allow access for?non-privileged processes Joerg Roedel
2010-04-09 17:43 ` [PATCH 0/1] uio_pci_generic: extensions to allow access for non-privileged processes Avi Kivity
2010-04-09 20:09 ` [PATCH 0/1] uio_pci_generic: extensions to allow access for?non-privileged processes Chris Wright
2010-04-09 20:05 ` [PATCH 0/1] uio_pci_generic: extensions to allow access for non-privileged processes Chris Wright
2010-04-01 21:27 ` Tom Lyon
2010-04-02 6:44 ` Avi Kivity
2010-04-01 12:52 ` Joerg Roedel
2010-04-01 15:40 ` Tom Lyon
2010-04-01 16:07 ` Joerg Roedel
2010-04-01 19:18 ` Tom Lyon
2010-04-01 20:09 ` Joerg Roedel [this message]
2010-04-01 14:25 ` Michael S. Tsirkin
2010-04-01 16:02 ` Tom Lyon
2010-04-01 16:57 ` Joerg Roedel
2010-04-01 19:08 ` Hans J. Koch
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