Re: [Xen-devel] [PATCH 4/7] vtd: add lookup_page method to iommu_ops

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.03.18 at 11:19, <Paul.Durrant@xxxxxxxxxx> wrote:
>> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
>> Sent: 15 March 2018 16:54
>> 
>> >>> On 12.02.18 at 11:47, <paul.durrant@xxxxxxxxxx> wrote:
>> > This patch adds a new method to the VT-d IOMMU implementation to find
>> the
>> > MFN currently mapped by the specified BFN. This functionality will be used
>> > by a subsequent patch.
>> 
>> How come this is VT-d only? The same is going to be needed at least
>> for the AMD IOMMU. And if you don't do it for ARM, then the hook
>> should be x86-specific for the time being.
> 
> I only have VT-d h/w to test on so it seemed prudent to keep it limited to 
> that. I did look at doing a speculative implementation for AMD but it was not 
> sufficiently obvious to give me confidence.
> I don't see any particular reason to keep the hook arch specific though... 
> it would just create code churn later, assuming someone wants to do PV-IOMMU 
> for ARM.

Well, the primary concern - as you're certainly aware - is the
dangling NULL pointer resulting from the lack of those other
implementations.

Jan


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