Re: [Xen-devel] [PATCH] AMD/guest_iommu: Disable guest iommu support

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 06/10/14 08:59, Jan Beulich wrote:
>>>> On 06.10.14 at 08:46, <Suravee.Suthikulpanit@xxxxxxx> wrote:
>> The function guest_iommu_set_base() was added by Wei before my time. I 
>> checked the log and didn't see the evidence that this code has ever been 
>> used. Do you remember why he added this code to begin with, and how this 
>> was planned to be used?
> The plan here clearly was to allow guests to see a virtual IOMMU,
> and the setting of the respective base address would then be
> a requirement for tool stack and/or virtual firmware to set up the
> environment for the guest.
>
> Jan
>

The commit which introduces the virtual IOMMU (c/s 4547137c3) indicates
that a virtual IOMMU is necessary for correct functioning of ATS-capable
guest device drivers using PASID or PRI, in passthrough.

~Andrew

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