> -----Original Message-----
> From: xen-users-bounces@lists.xensource.com
> [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of
> Andre.Weidemann@web.de
> Sent: 08 December 2006 14:43
> To: xen-users@lists.xensource.com
> Subject: [Xen-users] 3D acceleration question (again)
>
> Hi,
> I know this subject has been discussed several times here on the list
> before, but I''d like to bring it up again.
>
> From what I have read in the Wiki''s FAQ and the list here, an
IOMMU
> would cure the problem of translating the IO-Addresses for
> accessing the
> GFX card directly.
>
> From what I have read, the Pacifica architecture inside the AMD
> Athlon64s respectively the CPU''s northbridge provides an IOMMU.
> Is this correct?
Not quite. There is a possibility to use the GART (Graphics Aperture Redirection
Table(??)) to translate one PCI (including PCI, PCI-x, PCI-e and AGP[248]x)
address to another physical memory address - this is used in the Linux kernel to
do IOMMU for memory buffers above 4GB to hardware that isn''t 64-bit
addressing.
I think Mark Langsdorf at AMD was working on a xenified version of this, but I
don''t know what happened to that work. Unforutnately, the GART only
translates for ONE GUEST AT A TIME, so if you have a multiprocessor (or even
multicore) system, you can''t have two guests use the GART translation
(no problem in this application, you''d probably only _WANT_ give the
graphics card to ONE guest anyways) which limits it''s usefulness.
There are plans for a FULL IOMMU (actually, I''d expect this to be more
than a plan at this stage, but I don''t know what the hardware guys are
doing on this, and _IF_ I did know, I couldn''t tell anyone anyways...
;-) )
> Could this be used for the previously discussed address translations?
> If so, are there any plans yet on using this unit and could one get
> direct access to the GFX card so full hardware acceleration
> was possible?
As I said, there''s been plans for it, but as of right now I
don''t know if it''s realistic to expect this to happen.
--
Mats>
>
> Thank you in advance.
> André
>
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