Re: [Xen-devel] [RFC] xen/arm: Handling cache maintenance instructions by set/way

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 08.12.17 at 15:38, <julien.grall@xxxxxxxxxx> wrote:
> On 08/12/17 08:03, Tim Deegan wrote:
>> It should be possible to do something like the misconfigured-entry bit
>> trick by _allocating_ the memory up-front and building the p2m entries
>> but only making them usable by the {IO}MMUs on first access.  That
>> would make these early p2m walks shorter (because they can skip whole
>> subtrees that aren't marked present yet) without making major changes
>> to domain build or introducing run-time failures.
> 
> I am not aware of any way on Arm to misconfigure an entry. We do have 
> valid and access bits, although they will affect the IOMMU as well. So 
> it will not be possible to get page-table sharing with this "feature" 
> enabled.

How would you intend to solve the IOMMU part of the problem with
PoD? As was pointed out before - IOMMU and PoD are incompatible
on x86.

Jan


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