Re: [Xen-devel] [RFC PATCH 9/9] xen: Add use_iommu flag to createdomain domctl

[Oleksandr Tyshchenko <olekstysh@xxxxxxxxx>]

Hi, Ian

On Wed, Apr 26, 2017 at 1:05 PM, Ian Jackson <ian.jackson@xxxxxxxxxxxxx> wrote:
> Oleksandr Tyshchenko writes ("Re: [RFC PATCH 9/9] xen: Add use_iommu flag to 
> createdomain domctl"):
>> On Tue, Apr 25, 2017 at 6:23 PM, Wei Liu <wei.liu2@xxxxxxxxxx> wrote:
>> > Let me explain where I'm coming from:
>> >
>> > 1. if not populating the iommu page table causes Xen to malfunction
>> >    (crash?), it is a bug. It should be fixed without involvement
>> >    from toolstack.
>> > 2. if this is an optimasation, can't we not always populate iommu pt
>> >    hence no new flag is needed?
>> >
>> > Overall I'm not too convinced a new flag is needed.
>>
>> We don't want to always populate IOMMU page table since it might be
>> just wasting CPU and memory resources if no devices are assigned to
>> domain. That's why we need this hint.
>
> I thought we already had a way to tell libxl that pci passthrough is
> expected for this domain.  There are other things that want to know
> this in advance.  I can't seem to find it now at least in the docs,
> though.
Did mean a way different from the guest configuration file?

>
> Ian.



-- 
Regards,

Oleksandr Tyshchenko

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