Re: [Xen-devel] [PATCH] VTD/Intremap: Disable Intremap on Chipset 5500/5520/X58 due to errata

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.01.13 at 00:27, Malcolm Crossley <malcolm.crossley@xxxxxxxxxx> wrote:
> Unfortunately this chipset is very common and many BIOSes are not
> disabling remapping.  We can detect this in Xen and prevent turning on
> remapping in the first place.  However, this will turn VT-d off on many
> systems by default.

Why would the IOMMU be turned off in that case as a whole?
Interrupt remapping is not a prerequisite iirc.

> Users who still wish to use VT-d can use iommu=force if they are happy
> exposing the associated security risk.

"iommu=force" doesn't enable interrupt remapping if it was
forcibly turned off.

Jan


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