Re: [Xen-devel] dom0 / hypervisor hang on dom0 boot

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 20.05.13 at 16:30, "Dugger, Donald D" <donald.d.dugger@xxxxxxxxx> wrote:
> The only trick for i915 in dom0, in my mind, is to have CONFIG_DMAR enabled in
> dom0 although dom0 is not actually exposed with a VT-d engine. This sets 
> need_dmar
> flag in i915, ensures i915 to use Xen DMA interface instead of virt_to_phys, 
> so that
> MFN is written to GTT entries. Otherwise, having GPFN in GTT entries is 
> bogus, since
> GPU will DMA to wrong locations then, and thus cause random issues.

Enabling CONFIG_DMAR (or really CONFIG_INTEL_IOMMU in recent
kernels) is not an option. However, we patch all respective sites to
also take effect on Xen (of course that doesn't help pv-ops, but here
we're talking about a forward ported kernel anyway).

> Once we also identified a regression in 3.8, where need_dmar is not honored in
> i915 driver:

Dietmar had already tested with 3.9, so this ought to not affect
him.

Jan


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