AFAIK dom0 is pv-domain.
All interrupts are handled by xen and passed down to dom0 via events (kinda internal  xen interrupt-like stuff). PV kernel accepts them and process as normal interrupts.

Is Xen use IOMMU to protect itself from misbehave devices or not... I'm not sure.

On 11.10.2012 10:16, maheen butt wrote:
Hi all,

I'm investigating the source code of Xenified kernel. From documentations related to
Xen told me that all guest domains run in less privilege mode ( ring 1 in case of x86).
Dom0 is also running in ring 1. But it can have direct access to IO devices. It means
Dom0 has a special bahaviour that it is running in ring1 but can directly access IO devices.
How Dom0 access IO devices directly?
how can I relate this special way of Dom0 with its source code?


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