Re: [PATCH 2/5] mmu_notifier: keep track of active invalidation ranges

[Rik van Riel]

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On 11/03/2014 03:42 PM, j.glisse@xxxxxxxxx wrote:
> From: JÃrÃme Glisse <jglisse@xxxxxxxxxx>
> 
> The mmu_notifier_invalidate_range_start() and 
> mmu_notifier_invalidate_range_end() can be considered as forming
> an "atomic" section for the cpu page table update point of view. 
> Between this two function the cpu page table content is unreliable
>  for the address range being invalidated.
> 
> Current user such as kvm need to know when they can trust the 
> content of the cpu page table. This becomes even more important to 
> new users of the mmu_notifier api (such as HMM or ODP).
> 
> This patch use a structure define at all call site to 
> invalidate_range_start() that is added to a list for the duration 
> of the invalidation. It adds two new helpers to allow querying if
> a range is being invalidated or to wait for a range to become
> valid.
> 
> For proper synchronization, user must block new range invalidation 
> from inside there invalidate_range_start() callback, before
> calling the helper functions. Otherwise there is no garanty that a
> new range invalidation will not be added after the call to the
> helper function to query for existing range.
> 
> Signed-off-by: JÃrÃme Glisse <jglisse@xxxxxxxxxx>

Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>

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