RE: [Xen-users] AMD or Intel?

["Joop Boonen" <joop_boonen@xxxxxx>]

Hello Mats,

Is the IOMMU the one mentioned in this artikle?
http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/34434.pdf
http://www.amd.com/us-en/Corporate/VirtualPressRoom/0,,51_104_543~117440,00.html

If so, in which processor/core will it be available?

Regards,

Joop Boonen.


See also:
http://www.xensource.com/files/xs0106_xen_iommu.pdf


What does in this artikle
http://www.theinquirer.net/default.aspx?article=16879 the IOMMU mean?

<quote>
?Software IOTLB ? Intel® EM64T does not support an IOMMU in hardware while
AMD64 processors do. This means that physical addresses above 4GB (32
bits) cannot reliably be the source or destination of DMA operations.
Therefore, the Red Hat Enterprise Linux 3 Update 2 kernel "bounces" all
DMA operations to or from physical addresses above 4GB to buffers that the
kernel pre-allocated below 4GB at boot time. This is likely to result in
lower performance for IO-intensive workloads for Intel® EM64T as compared
to AMD64 processors.?
</quote>

On Fri, May 25, 2007 12:51 pm, Petersson, Mats wrote:
>> On a somewhat related topic, my understanding is that
>> Barcelona/K10 will
>> provide hardware (IO-MMU?) that will allow expansion cards (PCI, AGP,
>> PCIe, etc.) to be virtualised. Currently, if an expansion card were to
>> attempt to access RAM in a guest it would be accessing the RAM at that
>> address in the host, i.e., memory accesses in guests are not mapped to
>> the appropriate memory in the host. Is it true that Barcelona/K10 will
>> provide functionality to solve this problem? If so, has any work been
>> done on supporting this hardware in Xen?
>
> Sorry to disappoint, the upcoming "barcelona" core will have some
> improvements to the AMD-V implementation, in particular the nested
> paging feature, but I can clearly say that it doesn't have IOMMU.
>
> Nested paging allows the guest to run without intercepts of the
> page-table-updates, avoiding the code handling "shadow paging"
> altogether. It will speed up most HVM guests, particularly those that do
> a lot of page-table updates (such as creating/destroying processes a lot
> - kernel compile for example).
>
> The work to support IOMMU in Xen will happen when we're closer to having
> hardware with support for this.
>
> I'm not entirely sure (nor could I really tell anyone anyways) when the
> IOMMU will be available, but it's very unlikely to happen this year, I
> would think.
>
> --
> Mats
>
>
>
> _______________________________________________
> Xen-users mailing list
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> http://lists.xensource.com/xen-users
>



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