RE: [Xen-users] AMD or Intel?

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

> 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



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