Re: [Xen-devel] [PATCH 6/7] x86: add iommu_op to query reserved ranges

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 23.02.18 at 06:23, <kevin.tian@xxxxxxxxx> wrote:
>>  From: Paul Durrant [mailto:Paul.Durrant@xxxxxxxxxx]
>> Sent: Tuesday, February 13, 2018 5:25 PM
>> > From: Tian, Kevin [mailto:kevin.tian@xxxxxxxxx]
>> > Sent: 13 February 2018 06:52
>> > > From: Paul Durrant
>> > > Sent: Monday, February 12, 2018 6:47 PM
>> > > +    }
>> > > +
>> > > +    ctxt->nr_entries++;
>> > > +
>> > > +    return 1;
>> > > +}
>> > > +
>> > > +static int iommuop_query_reserved(struct
>> > > xen_iommu_op_query_reserved *op)
>> >
>> > I didn't get why we cannot reuse existing XENMEM_reserved_
>> > device_memory_map?
>> >
>> 
>> This hypercall is not intended to be tools-only. That one is, unless I 
>> misread
>> the #ifdefs.
>> 
> 
> I didn't realize it. Curious how Xen enforces such tools-only policy? What
> would happen if calling it from Dom0 kernel? I just felt not good of
> creating a new interface just for duplicated purpose...

It's not enforced for Dom0; Dom0 (including its kernel) is trusted.
How would Xen know whether a request came from user land
(through the privcmd driver) or directly from some kernel component?

Jan


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